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Assuming you can't use LINQ for whatever reason, is it a better practice to place your queries in stored procedures, or is it just as good a practice to execute ad hoc queries against the database (say, SQL Server for argument's sake)?
In my experience writing mostly WinForms Client/Server apps these are the simple conclusions I've come to:
Use Stored Procedures:
For any complex data work. If you're going to be doing something truly requiring a cursor or temp tables it's usually fastest to do it within SQL Server.
When you need to lock down access to the data. If you don't give table access to users (or role or whatever) you can be sure that the only way to interact with the data is through the SP's you create.
Use ad-hoc queries:
For CRUD when you don't need to restrict data access (or are doing so in another manner).
For simple searches. Creating SP's for a bunch of search criteria is a pain and difficult to maintain. If you can generate a reasonably fast search query use that.
In most of my applications I've used both SP's and ad-hoc sql, though I find I'm using SP's less and less as they end up being code just like C#, only harder to version control, test, and maintain. I would recommend using ad-hoc sql unless you can find a specific reason not to.
I can't speak to anything other than SQL Server, but the performance argument is not significantly valid there unless you're on 6.5 or earlier. SQL Server has been caching ad-hoc execution plans for roughly a decade now.
I think this is a basic conflict between people who must maintain the database and people who develop the user interfaces.
As a data person, I would not consider working with a database that is accessed through adhoc queries because they are difficult to effectively tune or manage. How can I know what affect a change to the schema will have? Additionally, I do not think users should ever be granted direct access to the database tables for security reasons (and I do not just mean SQL injection attacks, but also because it is a basic internal control to not allow direct rights and require all users to use only the procs designed for the app. This is to prevent possible fraud. Any financial system which allows direct insert, update or delete rights to tables is has a huge risk for fraud. This is a bad thing.).
Databases are not object-oriented and code which seems good from an object-oriented perspective is can be extremely bad from a database perspective.
Our developers tell us they are glad that all our databse access is through procs becasue it makes it much faster to fix a data-centered bug and then simply run the proc on the production environment rather than create a new branch of the code and recompile and reload to production. We require all our procs to be in subversion, so source control is not an issue at all. If it isn't in Subversion, it will periodically get dropped by the dbas, so there is no resistance to using Source Control.
Stored procedures represent a software contract that encapsulates the actions taken against the database. The code in the procedures, and even the schema of the database itself can be changed without affecting compiled, deployed code, just so the inputs and outputs of the procedure remain the same.
By embedding queries in your application, you are tightly coupling yourself to your data model.
For the same reason, it is also not good practice to simply create stored procedures that are just CRUD queries against every table in your database, since this is still tight coupling. The procedures should instead be bulky, coarse grained operations.
From a security perspective, it is good practice to disallow db_datareader and db_datawriter from your application and only allow access to stored procedures.
Stored procedures are definitely the way to go...they are compiled, have execution plan before hand and you could do rights management on them.
I do not understand this whole source control issue on stored procedure. You definitely can source control them, if only you are a little disciplined.
Always start with a .sql file that is the source of your stored procedure. Put it in version control once you have written your code. The next time you want to edit your stored procedure get it from your source control than your database. If you follow this, you will have as good source control as your code.
I would like to quote Tom Kyte from Oracle here...Here's his rule on where to write code...though a bit unrelated but good to know I guess.
Start with stored procedures in PL/SQL...
If you think something can't be done using stored procedure in PL/SQL, use Java stored procedure.
If you think something can't be done using Java Stored procedure, consider Pro*c.
If you think you can't achieve something using Pro*C, you might want to rethink what you need to get done.
My answer from a different post:
Stored Procedures are MORE maintainable because:
You don't have to recompile your C# app whenever you want to change some SQL
You end up reusing SQL code.
Code repetition is the worst thing you can do when you're trying to build a maintainable application!
What happens when you find a logic error that needs to be corrected in multiple places? You're more apt to forget to change that last spot where you copy & pasted your code.
In my opinion, the performance & security gains are an added plus. You can still write insecure/inefficient SQL stored procedures.
Easier to port to another DB - no procs to port
It's not very hard to script out all your stored procedures for creation in another DB. In fact - it's easier than exporting your tables because there are no primary/foreign keys to worry about.
In our application, there is a layer of code that provides the content of the query (and is sometimes a call to a stored procedure). This allows us to:
easily have all the queries under version control
to make what ever changes are required to each query for different database servers
eliminates repetition of the same query code through out our code
Access control is implemented in the middle layer, rather than in the database, so we don't need stored procedures there. This is in some ways a middle road between ad hoc queries and stored procs.
There are persuasive arguments for both - stored procedures are all located in a central repository, but are (potentially) hard to migrate and ad hoc queries are easier to debug as they are with your code, but they can also be harder to find in the code.
The argument that stored procedures are more efficient doesn't hold water anymore.
link text
Doing a google for Stored Procedure vs Dynamic Query will show decent arguments either way and probably best for you to make your own decision...
Store procedures should be used as much as possible, if your writing SQL into code your already setting yourself up for headaches in the futures. It takes about the same time to write a SPROC as it does to write it in code.
Consider a query that runs great under a medium load but once it goes into fulltime production your badly optimized query hammers the system and brings it to a crawl. In most SQL servers you are not the only application/service that is using it. Your application has now brought a bunch of angry people at your door.
If you have your queries in SPROCs you also allow your friendly DBA to manage and optimize with out recompiling or breaking your app. Remember DBA's are experts in this field, they know what to do and not do. It makes sense to utilise their greater knowledge!
EDIT: someone said that recompile is a lazy excuse! yeah lets see how lazy you feel when you have to recompile and deploy your app to 1000's of desktops, all because the DBA has told you that your ad-hoc Query is eating up too much Server time!
someone said that recompile is a lazy excuse! yeah lets see how lazy you feel when you have to recompile and deploy your app to 1000's of desktops, all because the DBA has told you that your ad-hoc Query is eating up too much Server time!
is it good system architecture if you let connect 1000 desktops directly to database?
Some things to think about here: Who Needs Stored Procedures, Anyways?
Clearly it's a matter of your own needs and preferences, but one very important thing to think about when using ad hoc queries in a public-facing environment is security. Always parameterize them and watch out for the typical vulnerabilities like SQL-injection attacks.
Stored Procedures are great because they can be changed without a recompile. I would try to use them as often as possible.
I only use ad-hoc for queries that are dynamically generated based on user input.
Procs for the reasons mentioned by others and also it is easier to tune a proc with profiler or parts of a proc. This way you don't have to tell someone to run his app to find out what is being sent to SQL server
If you do use ad-hoc queries make sure that they are parameterized
Parametized SQL or SPROC...doesn't matter from a performance stand point...you can query optimize either one.
For me the last remaining benefit of a SPROC is that I can eliminate a lot SQL rights management by only granting my login rights to execute sprocs...if you use Parametized SQL the login withing your connection string has a lot more rights (writing ANY kind of select statement on one of the tables they have access too for example).
I still prefer Parametized SQL though...
I haven't found any compelling argument for using ad-hoc queries. Especially those mixed up with your C#/Java/PHP code.
The sproc performance argument is moot - the 3 top RDBMs use query plan caching and have been for awhile. Its been documented... Or is 1995 still?
However, embedding SQL in your app is a terrible design too - code maintenance seems to be a missing concept for many.
If an application can start from scratch with an ORM (greenfield applications are far and few between!) its a great choice as your class model drives your DB model - and saves LOTS of time.
If an ORM framework is not available we have taken a hybrid of approach of creating an SQL resource XML file to look up SQL strings as we need them (they are then cached by the resource framework). If the SQL needs any minor manipulation its done in code - if major SQL string manipulation is needed we rethink the approach.
This hybrid approach lends to easy management by the developers (maybe we are the minority as my team is bright enough to read a query plan) and deployment is a simple checkout from SVN. Also, it makes switching RDBMs easier - just swap out the SQL resource file (not as easy as an ORM tool of course, but connecting to legacy systems or non-supported database this works)
Depends what your goal is. If you want to retrieve a list of items and it happens once during your application's entire run for example, it's probably not worth the effort of using a stored procedure. On the other hand, a query that runs repeatedly and takes a (relatively) long time to execute is an excellent candidate for database storage, since the performance will be better.
If your application lives almost entirely within the database, stored procedures are a no-brainer. If you're writing a desktop application to which the database is only tangentially important, ad-hoc queries may be a better option, as it keeps all of your code in one place.
#Terrapin: I think your assertion that the fact that you don't have to recompile your app to make modifications makes stored procedures a better option is a non-starter. There may be reasons to choose stored procedures over ad-hoc queries, but in the absence of anything else compelling, the compile issue seems like laziness rather than a real reason.
My experience is that 90% of queries and/or stored procedures should not be written at all (at least by hand).
Data access should be generated somehow automaticly. You can decide if you'd like to staticly generate procedures in compile time or dynamically at run time but when you want add column to the table (property to the object) you should modify only one file.
I prefer keeping all data access logic in the program code, in which the data access layer executes straight SQL queries. On the other hand, data management logic I put in the database in the form of triggers, stored procedures, custom functions and whatnot. An example of something I deem worthy of database-ifying is data generation - assume our customer has a FirstName and a LastName. Now, the user interface needs a DisplayName, which is derived from some nontrivial logic. For this generation, I create a stored procedure which is then executed by a trigger whenever the row (or other source data) is updated.
There appears to be this somewhat common misunderstanding that the data access layer IS the database and everything about data and data access goes in there "just because". This is simply wrong but I see a lot of designs which derive from this idea. Perhaps this is a local phenomonon, though.
I may just be turned off the idea of SPs after seeing so many badly designed ones. For example, one project I participated in used a set of CRUD stored procedures for every table and every possible query they encountered. In doing so they simply added another completely pointless layer. It is painful to even think about such things.
These days I hardly ever use stored procedures. I only use them for complicated sql queries that can't easily be done in code.
One of the main reasons is because stored procedures do not work as well with OR mappers.
These days I think you need a very good reason to write a business application / information system that does not use some sort of OR mapper.
Stored procedure work as block of code so in place of adhoc query it work fast.
Another thing is stored procedure give recompile option which the best part of
SQL you just use this for stored procedures nothing like this in adhoc query.
Some result in query and stored procedure are different that's my personal exp.
Use cast and covert function for check this.
Must use stored procedure for big projects to improve the performance.
I had 420 procedures in my project and it's work fine for me. I work for last 3 years on this project.
So use only procedures for any transaction.
is it good system architecture if you
let connect 1000 desktops directly to
database?
No it's obviously not, it's maybe a poor example but I think the point I was trying to make is clear, your DBA looks after your database infrastructure this is were their expertise is, stuffing SQL in code locks the door to them and their expertise.
Related
I have read many strong views (both for and against) SPs or DS.
I am writing a query engine in C++ (mySQL backend for now, though I may decide to go with a C++ ORM). I cant decide whether to write a SP, or to dynamically creat the SQL and send the query to the db engine.#
Any tips on how to decide?
Here's the simple answer:
If your programmers do both database and coding work, keep the SQL with the app. It's easier to maintain that way. Otherwise, let the DB guys handle it in SPs.
You have more control over the mechanisms outside the database. The biggest win for taking care of this outside the database is simply maintenance (in my mind). It'd be slightly hard to version control the SP vs the code you generate outside the database. One more thing to keep track of.
While we're on the topic, it's similar to handling data/schema migrations. It's annoyingly complex to version/handle schema migrations, if you don't already have a mechanism for this, you will have yet another thing you'll need to manage. It comes down to simply being easier to manage/version these things outside the database.
Consider the scenario where you have a bug in your SP. Now it needs to be changed, but then you hop over to another developers database/sandbox. What version is the sandbox and the SP? Now you have to track multiple versions.
One of the main differentiators is whether you are writing the "one true front end" or whether the database is the central piece of your application.
If you are going to have multiple front ends stored procedures make a lot of sense because you reduce your maintenance overhead. If you are writing only one interface, stored procedures are a pain, because you lose a lot of flexibility in changing your data set as your front end needs change, plus you now have to do code maintenance, version control, etc. in two places. Databases are a real pain to keep in sync with code repositories.
Finally, if you are coding for multiple databases (Oracle and SQL compatible code, for example), I'd avoid stored procedures completely.
You may in certain rare circumstances, after profiling, determine that some limited stored procedures are useful to you. This situation comes up way less than people think it does.
The main scenarios when you MUST have the SP is:
1) When you have very complex set of queries with heavy compile overhead and data drift low enough that recompiling is not needed on a regular basis.
2) When the "Only True" logic for accessing the specific data set is VERY complicated, needs to be accessed from several different codebases on different platforms (so writing multiple APIs in code is much more expensive).
Any other scenario, it's debatable, and can be decided one way or another.
I must also say that the other posters' arguments about versioning are not really such a big deal in my experience - having your SPs in version control is as easy as creating a "sql/db_name" directory structure and having easy basic "database release" script which releases the SP code from the version control location to the database. Every company I worked for had some kind of setup like this, central one run by DBAs or departmental one run by developers.
The one thing you want to avoid is to have your business logic spread across multiple tiers of your application. Database DDL and DML are difficult enough to keep in sync with an application code base as it is.
My recommendation is to create a good relational schema, but all your constraints and triggers so that the data retains integrity even if somebody goes to the database and tries to do something through some command line SQL.
Put all your business logic in an application or service that calls (static/dynamic) SQL then wraps the business functionality you are are trying to expose.
Stored-procedures have two purposes that I can think of.
An aid to simplifying data access.
The Stored Procedure does not have
any business logic in it, it just
knows about the structure of the
data and exposes an interface to
isolate accessing three tables and a
view just to get a single piece of
information.
Mapping the Domain Model to the Data
Model, Stored Procedures can assist
in making the Data Model look like a
given Domain Model.
After the program has been completed and has been profiled there are often performance issues with the pre 1.0 release. Stored procedures do offer batching of SQL without traffic needing to go back and forth between the DBMS and the Application. That being said in rare and extreme cases due to performance a few business rules might need to be migrated to the Stored-Procedure side. Make sure to document any exceptions to the architectural philosophy in multiple prominent places.
Stored Procedures are ideal for:
Creating reusable abstractions over complex queries;
Enforcing specific types of insertions/updates to tables (if you also deny permissions to the table);
Performing privileged operations that the logged-in user wouldn't normally be allowed to do;
Guaranteeing a consistent execution plan;
Extending the capabilities of an ORM (batch updates, hierarchy queries, etc.)
Dynamic SQL is ideal for:
Variable search arguments or output columns:
Optional search conditions
Pivot tables
IN clauses with user-specified values
ORM implementations (most can use SPs, but can't be built entirely on them);
DDL and administrative scripts.
They solve different problems, really. Use whichever one is more appropriate to the task at hand, and don't restrict yourself to just one or the other. After you work on database code for a while you'll start to get a more intuitive feel for these things; you'll find yourself banging together some rat's nest of strings for a query and think, "this should really go in a stored procedure."
Final note: Because this question implies a certain level of inexperience with SQL, I feel obliged to say, don't forget that you still need to parameterize your queries when you write dynamic SQL. Parameters aren't just for stored procedures.
DS is more flexible. SP approach makes your system more manageable.
I'm pretty new to SQL world. Here are my questions:
What are the benefits of stored procedured over normal SQL statement in applications?
Does stored procedure help eliminates SQL injection?
In Microsoft SQL Server it is called stored procedure. How about in Oracle, MySQL, DB2, etc.?
Thanks for your explanation.
Stored procedures only directly prevent SQL injection if you call them in a paramerized way. If you still have a string in your app with the procedure name and concatenate parameters from user input to that string in your code you'll have still have trouble.
However, when used exclusively, stored procedures let you add some additional protection by making it possible for you to disable permissions to everything but the EXEC command. Aside from this, parameterized queries/prepared statements are normally cached by the server, and so are just like a stored procedure in nearly every respect.
In spite of this, stored procedures have two big advantages for larger enterprises:
They allow you to define an application interface for the database, so that the system can be shared between multiple applications without having to duplicate logic in those applications.
They move the sql code to the db, where you can easily have an experienced DBA tune, update, and otherwise maintain it, rather than application developers who often don't know exactly what they're doing with database code.
Of course, these advantages aren't without cost:
It's harder to track changes in source control
The database code is far separated from the code that uses it
Developer tools for managing many stored procedures are less than ideal (if you've ever open the stored procedures folder in management studio to find 200 procedures for a database, you know what I'm talking about here).
Some of the benefits that I consider when using stored procedures
Stored procedures encapsulate query code at the server, rather than inside your application. This allows you to make changes to queries without having to recompile your application.
Stored procedures can be used for more well defined application security. You can Deny all rights on the base tables, grant execute only on the procs. This gives you a much smaller security footprint to manage.
Stored procedures are compiled code. With the latest versions of MSSQL the server does a better job of storing execution plans - so this isn't as big of an issue as it used to be, but still something to consider
Stored procedures eliminate SQL injection risk ONLY when used correctly. Make sure to use the parameters the right way inside the stored proc - stored procs that are just executing concatenated dynamic SQL inside them aren't doing anyone any good.
For the most part yes, SQL injection is far less likely with a stored procedure. Though there are times when you want to pass a stored procedure some data that requires you to use dynamic SQL inside the stored procedure and then you're right back where you started. In this sense I don't see any advantage to them over using parameterized queries in programming languages that support them.
Personally I hate stored procedures. Having code in two disjointed places is a pain in the ass and it makes deploys that much more complicated. I don't advocate littering your code with SQL statements either however as this leads to it's own set of headaches.
I recommend a DAL layer implemented one of two ways.
My favorite, use an object
relational management system (ORM).
I've been working with nHibernate
and I absolutely love it. The
learning curve in steep but
definitely worth the payoff in my
opinion.
Some kind of mechanism for keeping
all your SQL code in one place.
Either some sort of query library
you select from or a really
structured set of classes that
design the SQL for you. I don't
recommend this way since it's
basically like building your own ORM
and odds are you don't have the time
to do it correctly.
Forget stored procedures. Use an ORM.
One way in which stored procedures (ones which do not use dynamic SQL) can make the whole application more secure is that you can now set the permissions at the stored procedure level and not at the table level. If you do all of your data access this way (and forbid dynamic sql!) this means users can not under any circumstances do amnything to the database that is not in a stored proc. Developers always want to say that their application code can protect against outside threats, but they seem to forget that inside threats are often far more serious and by allowing permissions at the table level, they are at the mercy of any user who can find a way to directly query the database outside the application (another reason why in large shops only two or three people at most have production rights to anything in the datbase, it limits who can steal information).
Any financial system that uses anything except stored procs for instance is completely open to internal fraud which is a violation of internal controls that should prevent fraud and would not pass a good audit.
Stored procedures allow you to store you sql code in a location outside of the application. this gives you the ability to:
Change the SQL Code without recompiling/redistrubuting the application
Have multiple applications use the same stored procedure to access the same data.
Restrict users from having access to read/write to tables directly in the database.
From a development perspective it also allows the DBAs/database programmers to work on sql code without having to go through application code to work on it. (separation of responsibilities essentially).
Do stored procedures protect against injection attacks? For the most part yes. In sql server you can create stored procedures which are not effective against this, mainly by using sp_executesql. Now this doesn't main that sp_executesql is a security hole, it just means that more precaution needs to be taken when using it.
This also does not mean that stored procedures are the only way to protect against this. You can use parameritized sql to accomplish the same task of protecting against sql injection.
I do agree with other people stored procedures can be cumbersome, but they have their advantages too. Where I work, we have probably 20 different production databases for various reasons (don't ask). I work on a subset of maybe three, and my teammate and I know those three really really well. How do stored procedures help us? People come to us and when they need to grab that information out of those databases, we can get it for them. We don't have to spend hours explaining the schemas and what data is de-normalized. It's a layer of abstraction which allows us to program the most efficient code against the databases we know. If this isn't the case for you, then maybe stored procedures aren't the way to go, but in some instances they can add a lot of value.
When should I be using stored procedures instead of just writing the logic directly in my application? I'd like to reap the benefits of stored procedures, but I'd also like to not have my application logic spread out over the database and the application.
Are there any rules of thumb that you can think of in reference to this?
Wow... I'm going to swim directly against the current here and say, "almost always". There are a laundry list of reasons - some/many of which I'm sure others would argue. But I've developed apps both with and without the use of stored procs as a data access layer, and it has been my experience that well written stored procedures make it so much easier to write your application. Then there's the well-documented performance and security benefits.
This depends entirely on your environment. The answer to the question really isn't a coding problem, or even an analysis issue, but a business decision.
If your database supports just one application, and is reasonably tightly integrated with it, then it's better, for reasons of flexibility, to place your logic inside your application program. Under these circumstances handling the database simply as a plain data repository using common functionality looses you little and gains flexibility - with vendors, implementation, deployment and much else - and many of the purist arguments that the 'databases are for data' crowd make are demonstratively true.
On the other hand if your are handling a corporate database, which can generally be identified by having multiple access paths into it, then it is highly advisable to screw down the security as far as you can. At the very least all appropriate constraints should enabled, and if possible access to the data should be through views and procedures only. Whining programmers should be ignored in these cases as...
With a corporate database the asset is valuable and invalid data or actions can have business-threatening consequences. Your primary concern is safeguarding the business, not how convenient access is for your coders.
Such databases are by definition accessed by more than one application. You need to use the abstraction that stored procedures offer so the database can be changed when application A is upgraded and you don't have the resource to upgrade application B.
Similarly the encapsulation of business logic in SPs rather than in application code allows changes to such logic to be implemented across the business more easily and reliably than if such logic is embedded in application code. For example if a tax calculation changes it's less work, and more robust, if the calculation has to be changed in one SP than multiple applications. The rule of thumb here is that the business rule should be implemented at the closest point to the data where it is unique - so if you have a specialist application then the logic for that app can be implemented in that app, but logic more widely applicable to the business should be implemented in SPs.
Coders who dive into religious wars over the use or not of SPs generally have worked in only one environment or the other so they extrapolate their limited experience into a cast-iron position - which indeed will be perfectly defensible and correct in the context from which they come but misses the big picture. As always, you should make you decision on the needs of the business/customers/users and not on the which type of coding methodology you prefer.
I tend to avoid stored procedures. The debugging tools tend to be more primitive. Error reporting can be harder (vs your server's log file) and, to me at least, it just seems to add another language for no real gain.
There are cases where it can be useful, particularly when processing large amounts of data on the server and of course for database triggers that you can't do in code.
Other than that though, I tend to do everything in code and treat the database as a big dump of data rather than something I run code on.
Consider Who Needs Stored Procedures, Anyways?:
For modern databases and real world
usage scenarios, I believe a Stored
Procedure architecture has serious
downsides and little practical
benefit. Stored Procedures should be
considered database assembly language:
for use in only the most performance
critical situations.
and Why I do not use Stored Procedures:
The absolute worst thing you can do,
and it's horrifyingly common in the
Microsoft development world, is to
split related functionality between
sproc's and middle tier code.
Grrrrrrrr. You just make the code
brittle and you increase the
intellectual overhead of understanding
a system.
I said this in a comment, but I'm going to say it again here.
Security, Security, SECURITY.
When sql code is embedded in your application, you have to expose the underlying tables to direct access. This might sound okay at first. Until you get hit with some sql injection that scrambles all the varchar fields in your database.
Some people might say that they get around this by using magic quotes or some other way of properly escaping their embedded sql. The problem, though, is the one query a dev didn't escape correctly. Or, the dev that forgot to not allow code to be uploaded. Or, the web server that was cracked which allowed the attacker to upload code. Or,... you get the point. It's hard to cover all your bases.
My point is, all modern databases have security built in. You can simply deny direct table access (select, insert, update, and deletes) and force everything to go through your s'procs. By doing so generic attacks will no longer work. Instead the attacker would have to take the time to learn the intimate details of your system. This increases their "cost" in terms of time spent and stops drive by and worm attacks.
I know we can't secure ourselves against everything, but if you take the time to architect your apps so that the cost to crack it far outweighs the benefits then you are going to serious reduce your potential of data loss. That means taking advantage of all the security tools available to you.
Finally, as to the idea of not using s'procs because you might have to port to a different rdbms: First, most apps don't change database servers. Second, in the event that it's a real possibility, you have to code using ANSI sql anyway; which you can do in your procs. Third, you would have to reevaluate all of your sql code no matter what and it's a whole lot easier when that code is in one place. Fourth, all modern databases now support s'procs. Fifth, when using s'proc's you can custom tune your sql for the database it's running under to take advantage of that particular database's sql extensions.
Basically when you have to perform operations involving data that do not need to get out of the database. For example, you want to update one table with data from another, it makes little sense to get the data out and then back in if you can do it all in one single shot to the db.
Another situation where it may be acceptable to use stored procedures is when you are 100% sure you will never deploy your application to another database vendor. If you are an Oracle shop and you have lots of applications talking to the same database it may make sense to have stored procedures to make sure all of them talk to the db in a consistent manner.
Complicated database queries for me tend to end up as stored procs. Another thought to consider is that your database might be completely separate and distinct from the application. Lets say you run an Oracle DB and you essentially are building an API for other application developers at your organization to call into. You can hide the complicated stuff from them and provide a stored proc in its place.
A very simple example:
registerUser(username, password)
might end up running a few different queries (check if it exists, create entries in a preference table, etc) and you might want to encapsulate them.
Of course, different people will have different perspectives (a DBA versus a Programmer).
I used stored procs in 1 of 3 scenarios:
Speed
When speed is of the utmost importance, stored procedures provide an excellent method
Complexity
When I'm updating several tables and the code logic might change down the road, I can update the stored proc and avoid a recompile. Stored procedures are an excellent black box method for updating lots of data in a single stroke.
Transactions
When I'm working an insert, delete or update that spans multiple tables. I wrap the whole thing in a transaction. If there is an error, it's very easy to roll back the transaction and throw an error to avoid data corruption.
The bottom 2 are very do-able in code. However, stored procedures provide an black-box method of working when complex and transaction level operations are important. Otherwise, stick with code level database operations.
Security used to be one of the reasons. However, with LINQ and other ORMs out there, code level DAL operations are much more secure than they've been in the past. Stored procs ARE secure but so are ORMs like LINQ.
We use stored procedures for all of our reporting needs. They can usually retrieve the data faster and in a way that the report can just spit out directly instead of having to do any kind of calculations or similar.
We also will use stored procedures for complex or complicated queries we need to do that would be difficult to read if they were otherwise inside of our codebase.
It can also be very useful as a matter of encapsulation and in the philosophy of DRY. For instance I use stored functions for calculations inside a table that I need for several queries inside the code. This way I use the better performance as well as the ensuring that the calculation is always done the same way.
I would not use it for higher functionality or logic the should be in the business logic layer of an architecture, but focused on the model layer, where the functionality is clearly focused on the database design and possible flexibility of changing the database design without breaking the API to the other layers.
I tend to always use stored procedures. Personally, I find it makes everything easier to maintain. Then there is the security and performance considerations.
Just make sure you write clean, well laid out and well documented stored procedures.
When all the code is in a stored proc, it is far easier to refactor the database when needed. Changes to logic are far easier to push as well. It is also far far easier to performance tune and sooner or later performance tuning becomes necessary for most database applications.
From my experience, stored procedures can be very useful for building reporting databases/pipelines, however, I'd argue that you should avoid using stored procedures within applications as they can impede a team's velocity and any security risks of building queries within an application can be mitigated by the use of modern tooling/frameworks.
Why might we avoid it?
To avoid tight-coupling between applications and databases. If we use stored procedures, we won't be able to easily change our underlying database in the future because we'd have to either:
Migrate stored procedures from one database (e.g. DB2) to another (e.g. SQL Server) which could be painstakingly time-consuming or...
Migrate all the queries to the applications themselves (or potentially in a shared library)
Because code-first is a thing. There a several ORMs which can enable us to target any database and even manage the table schemas without ever needing to touch the database. ORMs such as Entity Framework or Dapper allow developers to focus on building features instead of writing stored procedures and wiring them up in the application.
It's yet another thing that developers need to learn in order to be productive. Instead, they can write the queries as part of the applications which makes the queries far simpler to understand, maintain, and modify by the developers who are building new features and/or fixing bugs.
Ultimately, it depends on what developers are most comfortable with.
If a developer has a heavy SQL background, they might go with Stored Procs.
If a developer has lots of app development experience, they might prefer queries in code. Personally, I think having queries in code can enable developers to move much faster and security concerns can be mitigated by ensuring teams are following best practices (e.g. parameterized queries, ORM). Stored procs aren't a "silver bullet" for system security.
Does the use of procedures still make sense in 202X?
Maybe in low level and rare scenarios or if we write code for a legacy companies with unfounded restrictions, stored procedure should be an option.
If entire logic is in the database, should I need a dba to change it?
No. In modern platforms, the requirement of a DBA to change the business logic is not an option.
Hot modification of stored procedures without dev or staging phases, area a crazy idea.
How easy is to maintain a procedure with dozens of lines, cursors and other low level database features vs a OOP objects in any modern language in which a junior developer is able to maintain?
This answers itself
Hide tables from my development team for security reasons sounds very crazy for me, in these times in which agility and well documentation are everything.
Modern development team with a modern database, should not worry about security. What's more, they need access to sandbox version of database to reduce the time of its deliverables.
With modern ORMs, ESBs, ETLs and the constant increase of cpu power, stored procedures are not an option anymore. Should I invest time and money in these tools, to create at final: one big stored procedure?
Of course, not.
On top of the speed and security considerations, I tend to stick as much in Stored Procedures as possible for ease of maintenance and alterations. If you put the logic in your application, and find later that sql logic has an error or needs to work differently in some manner, you have to recompile and redeploy the whole app in many cases (especially if it's a client side app such as WPF, Win-Forms, etc). If you keep the logic in the stored proc, all you have to do is update the proc and you never have to touch the application.
I agree that they should be used often and well.
The use case I think is extremely compelling and extremely useful is if you are taking in a lot of raw information that should be separated out into several tables, where the some of the data may have records that already exist and need to be connected by foreign key id, then you can just IF EXISTS checks and insert if it doesn't or return key if it does, which makes everything more uniform, succinct, and maintainable in the long run.
The only case where I would suggest against using them is if you are doing a lot of logic or number crunching between queries which is best done in the app server OR if you are working for a company where keeping all of the logic in the code is important for maintainability/understanding what is happening. If you have a git repository full of everything anyone would need and is easily understandable, that can be very valuable.
The stored procedures are a method of collecting operations that should be done together on database side, while still keeping them on database side.
This includes:
Populating several tables from one rowsource
Checking several tables against different business rules
Performing operations that cannot be efficiently performed using set-based approach
etc.
The main problem with stored procedures is that they are hard to maintain.
You, therefore, should make stored procedures as easy to maintain as all your other code.
I have an article on this in my blog:
Schema junk
I've had some very bad experiences with this.
I'm not opposed to stored procedures in their place, but gratuitous use of stored procedures can be very expensive.
First, stored procedures run on the database server. That means that if you have a multi-server environment with 50 webservers and one database server, instead of spreading workloads over 50 cheap machines, you load up one expensive one (since the database server is commonly built as a heavyweight server). And you're risking creating a single-point-of-failure.
Secondly, it's not very easy to write an application solely in stored procedures, although I ran into one that made a superhuman effort to try to. So you end up with something that's expensive to maintain: It's implemented in 2 different programming languages, and the source code is often not all in one place either, since stored procedures are definitively stored in the DBMS and not in a source archive. Assuming that someone ever managed/bothered o pull them out of the database server and source-archive them at all.
So aside from a fairly messy app architecture, you also limit the set of qualified chimpanzees who can maintain it, as multiple skills are required.
On the other hand, stored procedures are extremely useful, IF:
You need to maintain some sort of data integrity across multiple systems. That is, the stored logic doesn't belong to any single app, but you need consistent behavior from all participating apps. A certain amount of this is almost inevitable in modern-day apps in the form of foreign keys and triggers, but occasionally, major editing and validation may be warranted as well.
You need performance that can only be achieved by running logic on the database server itself and not as a client. But, as I said, when you do that, you're eating into the total system resources of the DBMS server. So it behooves you to ensure that if there are significant bits of the offending operation that CAN be offloaded onto clients, you can separate them out and leave the most critical stuff for the DBMS server.
A particular scenario you're likely to benefit involves the situation around the "(n+1)" scalability problem. Any kind of multidimensional/hierarchical situation is likely to involve this scenario.
Another scenario would involve use cases where it does some protocol when handling the tables (hint: defined steps which transactions are likely to be involved), this could benefit from locality of reference: Being in the server, queries might benefit. OTOH, you could supply a batch of statements directly into the server. Specially when you're on a XA environment and you have to access federated databases.
If you are talking business logic rather than just "Should I use sprocs in general" I would say you should put business logic in sprocs when you are carrying out large set based operations or any other time executing the logic would require a large number of calls to the db from the app.
It also depends on your audience. Is ease of installation and portability across DBMSs important to you?
If your program should be easy to install and easy to run on different database systems then you should stay away from stored procedures and also look out for non-portable SQL in your code.
Should queries live inside the classes that need the data? Should queries live in stored procedures in the database so that they are reusable?
In the first situation, changing your queries won't affect other people (either other code or people generating reports, etc). In the second, the queries are reusable by many and only exist in one place, but if someone breaks them, they're broken for everyone.
I used to be big on the stored proc solution but have changed my tune in the last year as databases have gotten faster and ORMs have entered the main stream. There is certainly a place for stored procs. But when it comes to simple CRUD sql: one liner insert/update/select/delete, using an ORM to handle this is the most elegant solution in my opinion, but I'm sure many will argue the other way. An ORM will take the SQL and DB connection building plumbing out of your code and make the persistence logic much more fluidly integrated with your app.
I suggest placing them as stored procedures in the database. Not only will you have the re-use advantage but also you'll make sure the same query (being a select, update, insert, etc...) it is the same because you are using the same stored procedure. If you need to change it, you'll only change it in one place. Also, you'll be taking advantage of the database server's processing power instead of the server/computer where your application resides. That is my suggestion.
Good luck!
It depends / it's situational. There are very strong arguments for and against either option. Personally, I really don't like seeing business logic get split between the database (in stored procedures) and in code, so I usually want all the queries in code to the maximum extent possible.
In the Microsoft world, there are things like Reporting Services that can retrieve data from classes/objects instead of (and in addition to) a database / stored procedures. Also, there are things like Linq that give you more strongly typed queries in code. There are also strong, mature ORMs like NHibernate that allow for writing pretty much all types of queries from code.
That said, there are still times when you are doing "rowset" types of things with your queries that work much better in a stored procedure than they work from code.
In the majority of situations, either/both options work just fine.
From my perspective, I think that stored procs are the the way to go. First, they are easier to maintain as a quick change to one means just running the script not recompiling the application. Second they are far better for security. You can set permissions at the sp level and not directly on the tables and views. This helps prevent fraud because the users cannot do anything directly to the datbase that isn't specified in a stored proc. They are easier to performance tune. When you use stored procs, you can use the database dependency metadata to help determine the affect of database changes on the code base. In many systems, not all data access or or even CRUD operations will take place through the application, having the code there seems to me to be counterproductive. If all the data access is in one place (an idea I support), it should be in the database where it is accessible to all applications or processes that might need to use it.
I've found that application programmers often don't consider the best way for a database to process information as they are focused on the application not the backend. By putting the code for the database in the database where it belongs, it is more likely to be seen and reviewed by database specialists who do consider the database and it's perfomance. We support hundreds of databases and applications here. I can look in any database and find the code that I need to find when something is slow. I don't have to upload the application code for each of hundreds of different applications just to see the part I need to do my job.
First of all there is a partial question regarding this, but it is not exactly what I'm asking, so, bear with me and go for it.
My question is, after looking at what SubSonic does and the excellent videos from Rob Connery I need to ask: Shall we use a tool like this and do Inline queries or shall we do the queries using a call to the stored procedure?
I don't want to minimize any work from Rob (which I think it's amazing) but I just want your opinion on this cause I need to start a new project and I'm in the middle of the line; shall I use SubSonic (or other like tool, like NHibernate) or I just continue my method that is always call a stored procedure even if it's a simple as
Select this, that from myTable where myStuff = StackOverflow;
It doesn't need to be one or the other. If it's a simple query, use the SubSonic query tool. If it's more complex, use a stored procedure and load up a collection or create a dataset from the results.
See here: What are the pros and cons to keeping SQL in Stored Procs versus Code and here SubSonic and Stored Procedures
See answers here and here. I use sprocs whenever I can, except when red tape means it takes a week to make it into the database.
Stored procedures are gold when you have several applications that depend on the same database. It let's you define and maintain query logic once, rather than several places.
On the other hand, it's pretty easy for stored procedures themselves to become a big jumbled mess in the database, since most systems don't have a good method for organizing them logically. And they can be more difficult to version and track changes.
I wouldn't personally follow rigid rules. Certainly during the development stages, you want to be able to quickly change your queries so I would inline them.
Later on, I would move to stored procedures because they offer the following two advantages. I'm sure there are more but these two win me over.
1/ Stored procedures group the data and the code for manipulating/extracting that data at one point. This makes the life of your DBA a lot easier (assuming your app is sizable enough to warrant a DBA) since they can optimize based on known factors.
One of the big bugbears of a DBA is ad-hoc queries (especially by clowns who don't know what a full table scan is). DBAs prefer to have nice consistent queries that they can tune the database to.
2/ Stored procedures can contain logic which is best left in the database. I've seen stored procs in DB2/z with many dozens of lines but all the client has to code is a single line like "give me that list".
Because the logic for "that list" is stored in the database, the DBAs can modify how it's stored and extracted at will without compromising or changing the client code. This is similar to encapsulation that made object-orientd languages 'cleaner' than what came before.
I've done a mix of inline queries and stored procedures. I prefer more of the stored procedure/view approach as it gains a nice spot for you to make a change if needed. When you have inline queries you always have to go and change the code to change an inline query and then re-roll the application. You also might have the inline query in multiple places so you would have to change a lot more code than with one stored procedure.
Then again if you have to add a parameter to a stored procedure, your still changing a lot of code anyways.
Another note is how often the data changes behind the stored procedure, where I work we have third party tables that may break up into normalized tables, or a table becomes obsolete. In that case a stored procedure/view may minimize the exposure you have to that change.
I've also written a entire application without stored procedures. It had three classes and 10 pages, was not worth it at all. I think there comes a point when its overkill, or can be justified, but it also comes down to your personal opinion and preference.
Are you going to only ever access your database from that one application?
If not, then you are probably better off using stored procedures so that you can have a consistent interface to your database.
Is there any significant cost to distributing your application if you need to make a change?
If so, then you are probably better off using stored procedures which can be changed at the server and those changes won't need to be distributed.
Are you at all concerned about the security of your database?
If so, then you probably want to use stored procedures so that you don't have to grant direct access to tables to a user.
If you're writing a small application, without a wide audience, for a system that won't be used or accessed outside of your application, then inline SQL might be ok.
With Subsonic you will use inline, views and stored procedures. Subsonic makes data access easier, but you can't do everthing in a subsonic query. Though the latest version, 2.1 is getting better.
For basic CRUD operations, inline SQL will be straight forward. For more complex data needs, a view will need to be made and then you will do a Subsonic query on the view.
Stored procs are good for harder data computations and data retrieval. Set based retrieval is usually always faster then procedural processing.
Current Subsonic application uses all three options with great results.
I prefer inline sql unless the stored procedure has actual logic (variables, cursors, etc) involved. I have been using LINQ to SQL lately, and taking the generated classes and adding partial classes that have some predefined, common linq queries. I feel this makes for faster development.
Edit: I know I'm going to get downmodded for this. If you ever talk down on foreign keys or stored procedures, you will get downmodded. DBAs need job security I guess...
The advantages of stored procedure (to my mind)
The SQL is in one place
You are able to get query plans.
You can modify the database structure if necessary to improve performance
They are compiled and thus those query plans do not have to get constructed on the fly
If you use permissions - you can be sure of the queries that the application will make.
Stored procedures group the data and the code for manipulating/extracting that data at one point. This makes the life of your DBA a lot easier (assuming your app is sizable enough to warrant a DBA) since they can optimize based on known factors.
Stored procedures can contain logic which is best left in the database. I've seen stored procs in DB2/z with many dozens of lines but all the client has to code is a single line like "give me that list".
the best advantage of using stored procs i found is that when we want to change in the logic, in case of inline query we need to go to everyplace and change it and re- roll the every application but in the case of stored proc change is required only at one place.
So use inline queries when you have clear logic; otherwise prefer stored procs.