I wonder what are the advantages and disadvantages using one over the other. This question originated from an advice I got here: Allocate buffer dynamically for DB query according to the record actual size
I am looking for a list of the important differences (and not an exhaustive list) that will help me to make an educated decision.
I have working experience with win32::odbc and can testify genuinely about it. It will very helpful if someone can share his/hers experience on top of the ‘dry’ documented details.
Additional info:
The author of Win32::ODBC wrote here: http://www.roth.net/perl/odbc/docs/ODBC_Docs.htm - "There are several alternatives to Win32::ODBC available such as the DataBase Interface (DBI) version called DBD::ODBC. This ODBC Perl extension is available across different platforms such as Mac and UNIX. It is a good tool to use for ODBC access into databases although it lacks some of the functionality that Win32::ODBC has."
I wonder if you know what is the functionality that it lacks.
My main reasons with going for the DBI stack are flexibility and the broader population of testers/debuggers. With DBI you are allowing yourself the option of using a driver that is specifically tuned to your particular database engine. Yes, most databases also offer an ODBC driver, but some specific capabilities may be unavailable or more troublesome through that particular API. Additionally, DBI is platform independent, making any possible future porting to another OS that much less trouble. Lastly the population of folks using DBI for their database access far exceeds those using Win32::ODBC, meaning bugs are likely to be found & patched quicker.
Looking at your other linked question I notice you are using Oracle. Using DBI you'd have the choice between using DBD::ODBC or DBD::Oracle under the hood. You can make this choice with a simple change to one of the parameters of the DBI->connect method.
If you are using Oracle's Instant Client, using DBD::Oracle can save you the trouble of downloading/installing the ODBC component on machines that will only need access via Perl. Of course removing the ODBC layer from the equation may have benefits as well.
Update:
Win32::ODBC is a relatively direct conversion of the ODBC Middleware API from C to Perl. If you are willing to limit yourself to ODBC connections on Windows, this does have the relatively minor advantage of giving you more direct control of the ODBC Middleware layer that is controlling your underlying Database. This of course does not imply that the ODBC API is particularly faithful to the API and/or capabilities of the underlying Database.
Again, presuming that you're using Oracle, you seem to have 3 choices:
Win32::ODBC -> ODBC -> Oracle's Driver for ODBC ~> Oracle Client -> Oracle Server
DBI -> DBD::Oracle ~> Oracle Client -> Oracle Server
DBI -> DBD::ODBC ~> ODBC -> Oracle's Driver for ODBC ~> Oracle Client -> Oracle Server
Where the '~>' is to the right of a layer that needed to "shim" one API to fit another.
Now I can understand if you find API fidelity to the ODBC Middleware to be desirable. Personally, I'd rather have the flexibility of DBI & the shorter software stack used by DBD::Oracle. Though I'll also guess that the longer stack involving DBD::ODBC would suit 99+% of all needs, even with two shim layers.
Another difference between DBI & Win32::ODBC is that there are many modules built around the DBI stack. The entire DBIx namespace depends on it. Search for each of these modules on metacpan.org and click on the 'reverse dependencies' link on their page and you'll get a rather sharp picture of the relative value the Perl community has assigned to each.
So if you want an additional, purely selfish, reason: a Perl developer with experience in DBI will also find themselves in much greater demand. Seriously.
Related
In my CS program, I was told I should learn SQL for my databases.
If I'm using PostgreSQL, do I also need a SQL server to go along with it? Is PostgreSQL a language, a server, or both? Is there even a SQL language or is it only servers?
Background: I downloaded Postgres because hey, that has SQL in the name, it works and I'm under the impression it's a pretty good choice anyway. But I couldn't figure out through their website if it needs a companion server, so I went looking for one and found AWS RDS.
The impression I have is that Postgres is the language and AWS RDS is the server, and they serve different functions. But I'm not sure about any of that.
Seems you're learning too many new topics at the same time.
Ok. I'll try to answer.
SQL stands for 'Structured Query Language', and serves as a 'standard' for many vendors that in much ways respects its fundamentals. Oracle, MySQL (now owned by Oracle), MariaDB and PostreSQL are some vendors.
Main thing with SQL code I would recommend you to identify every time you look at it, is to understand if it belongs to DML or DDL. DML stands for 'Data Manipulation Language' and refers to SQL instructions which 'modifies' data. DDL stands for 'Data Declaration Language' which defines or 'alter' de structure on which data will be stored.
Another important concept is atomicity of data manipulation. You can confirm a change or roll it back before it is persisted. This thing corresponds to 'commit' changes or do a 'rollback'. It's some kind of advanced concept, but generally happens "automatically" with standard client configurations. Later, you would have to know about it while programming some system module which interacts with databases.
When you think of the SQL 'server', it refers to the software configured/installed which has the responsability of manage persistence of data within some kind of 'instance' of persistence, allocated in some system with data storage capabilities. AWS implements this service in the cloud, and RDS is the product which supports many kind of SQL flavors to choose (Oracle, Postgresql, etc.)
If you are comfortable with Docker, I recomend you learn the basics which would help you setup and destroy databases many times, which is useful to develop and test locally. Next command, let you start a Postgresql database configured with open port 5432. You can see the server log through docker and use some SQL client to get connected. When you press Ctrl+C everything will be deleted. Of course there are other ways to keep data persistent, but this command would be an easy starting point.
$ docker run --rm -p 5432:5432 --name some-postgres-container-name -e POSTGRES_PASSWORD=mysecretpassword postgres:13.3
Side note: it's better to get used to work with specific docker image versions always (not 'latest').
More details of it usage here: https://hub.docker.com/_/postgres/
if I'm using PostgreSQL, do I also need a SQL server to go along with
it? Is PostgreSQL a language, a server, or both? Is there even a SQL
language or is it only servers lol? I'm genuinely trying to figure
this out myself, but basically everything I read is beyond my scope of
competence and confuses me more. I'm learning the syntax of SQL well
enough, but I'm so confused about everything on the most fundamental
level.
By the way "SQL Server" is Microsoft's SQL flavor, just another one. Don't be confused with the concept of having some SQL server configured.
Yes, you can think of PostgreSQL as a language too, which shares most of its syntax and semantics with other SQL vendors. Yes, there is a 'basic' SQL language shared and compatible between all vendors; some share more aspects than others. In terms of Venn diagrams, you can think of many circles representing each one, Microsoft's SQL Server, Oracle SQL, PostgreSQL, MySQL, etc. sharing the very most of its elements, where each element is a SQL instruction.
When dealing with Databases in general, keep in mind that they helps to modelate situations of 'real world' scenarios or software systems. SQL allows to 'talk' to implementation of "Relational Databases" wich is one kind of database modeling, but there are others too. ER Diagrams helps to represent the 'structure' of a database in a conceptual manner. I like DBeaver because it has an integrated ER diagram generator wich helps to understand the structure of a given database instance.
I have used Postgres and it is an excellent product (and free).
I would install it standalone first. It does come with its own client tools, which you use to communicate with the database server, which runs independently as a service. However, you might be better off installing something like SqlWorkbench as a client tool (which I use). In the config you specify the machine Postgres is running on (which can be your local computer for testing purposes) and the port to connect on. Essentially, the client sends your instructions to Postgres server and the server returns the resultsets associated with your instructions. The client also formats the resultsets into a nice readable "spreadsheet" format with rows and columns.
First I'll try to answer the questions you asked. There is a SQL language, but in practice it is not strictly standardized. There are many offerings for databases and database servers. Many of these are discussed below.
Any database you pick will give you the chance to learn basics of SQL queries and this knowledge will serve you well even if you switch to a different database later.
Specifically, when it comes to PostgreSQL, it is a Relational Database Management System. It is a software that operates as a server. You can install it on your personal computer running Windows, Linux, or MacOS. You can also install in on a dedicated server computer where you'll get better performance and uptime. Further, there are many companies that offer PostgreSQL hosting including Amazon RDS and Google Cloud but they're not free.
For a CS student, PostreSQL installed on your personal computer might be a reasonable choice. But you have lots of options. Read on....
For a CS program, your choice of database will depend on:
what degree of portability you need
how much data you have
how many users will connect to database
what kinds of jobs you might pursue after graduation
Portability
If you think you want to ship your database with your application, then your best bet is probably SQLite. By some accounts it can handle several million rows worth of data and still be performant. However, it's not great if you need for multiple users to connect to the same database. Your data can get corrupted in many multi-user scenarios.
How Much Data and Users
For large data and large users, you'll want to consider the client/server heavy hitters:
PostgreSQL
MySQL/MariaDB
Oracle
SQL Server
These databases will support large quantities of data any many simultaneous connections. But if you want to distribute the database with your application, it's not a good idea. Or if you want to demonstrate your app, you need to ensure that a connection to a server will be available. All of these databases come with a free version, but the last two will have the most restrictions.
After Graduation
Now you're looking to the future and possibly what kind of skills you want to put on your resume. If you think you'll end up in a corporate environment that is already well established, they will likely already have a preferred database and it could be any of the ones listed here (SQLite or the "heavy hitters"). If you want to position yourself as developing apps with low overhead cost, you'll gravitate towards SQLite/PostgreSQL/MySQL. If you think you're going to be some kind of database administrator working in a buttoned-up corporate environment, those companies tend to favor SQL Server and Oracle.
Good luck. Any choice you make will probably be fine. Knowing some flavor of SQL is useful for your future endeavors.
SQL is a language like any other language but working on database. It is called SQL because it works on structured data like table (i.e rows and columns). After reading the documentation of PostgreSQL, I think we do not need any separate server installation. You can download it from here. If you are facing any issues with it I suggest using MySQL workbench. Although installation may take longer time, but its easy to understand.
Everybody loves to mention how JDBC abstracts away vendor-specific differences between SQLs to present a single SQL flavor that would work against a whole slew of them.
But no book or reference on JDBC ever mentions a (detailed) specification or even a decent, user-space coverage of this SQL supported by (a specific version of) JDBC, say JDBC 4.1!
So, what ends up happening (at least with me) is that, if I'm working with MySQL, I must refer to the MySQL reference manual and then try to guard myself against accidentally using MySQL-specific features. For writing portable SQL (at least at the level supported by the JDBC driver version I'm using), I would rather prefer to refer to a JDBC spec or to an SQL spec directly instead of referring to MySQL, PostgresQL, etc.
Is the SQL standard itself (2008, 2003, etc), on which a particular version of JDBC is based, freely available? Or, do I have to shell out $$ to get a copy?
There is no "JDBC SQL", just ISO SQL and the vendor implementations of it. JDBC defines the interface for talking to SQL databases, it's a different layer to the query language its self.
The reference for JDBC its self is the JSR documentation:
JDBC 4.0
JDBC 4.1
Unfortunately the official SQL standards are expensive and must be purchased from the ISO.
You can find late-stage drafts that're perfectly good for reference when you're not trying to develop a conforming implementation here among other places.
The SQL spec isn't the most friendly and readable of things, so in practice it's a good idea to use vendor documentation that's actually intended to be read by human beings. You can compare a couple of vendor docs or fall back on the standard doc when uncertainty arises.
Standard compliance with the spec isn't exactly ideal across DBs; writing code strictly to the spec doesn't necessarily mean it'll actually work. For example, MySQL doesn't impliment window functions or common table expressions, PostgreSQL doesn't implement SQL/PSM (instead offering PL/PgSQL) or the CALL statement; most vendors use different ways of specifying auto-increment columns or sequence generators; etc etc etc.
Please don't use the w3schools SQL guides, they're severely outdated, wrong, fail to differentiate between vendor extensions and the standard, and should generally be avoided. I mention them because w3schools tends to come up quite high in search rankings - back in the day they used to actually be useful.
You can download the JDBC 4.1 specification from http://download.oracle.com/otndocs/jcp/jdbc-4_1-mrel-spec/index.html but this only covers JDBC itself, not SQL. The specification is more a description of the interface; it does expect databases to support some level of the SQL standards, but don't expect to find more information than a reference to the SQL standard if it comes to the requirements to queries.
You usually need to use the database specific SQL anyway, because even though there is a SQL standard, database vendors don't implement them to the letter. JDBC itself defines some escapes to bridge the gaps, but as far as I know, they are hardly ever used. Drivers also - usually - don't translate standard SQL to database specific SQL if the database doesn't support the standard SQL.
If you want to look at the official SQL standard, you need to buy it from ISO or your country-specific ISO representative. That said, with some searching you can find and download draft versions of the specification for free. I am not sure how helpful that is though, as the SQL standard documents are not intended as a reference manual, but meant to be a formal description and goes really deep in details that are only relevant to an implementer.
Is there an option to comunicate a TVF/UDF in a DBMS with an external IDE or language like C? Doing it without writing to a table?
I know there is a way of 'memory mapping' or a way to share block of memory
POSIX mmap() function
Windows OpenFileMapping() function
I am using Windows, so Is there a way to communicate a DBMS using memory mapping or sharing with something like C?
But how would you avoid writing to a table, or a file, using just memory?
Shared Memory is available as a data transport to and from SQL providers. You don't have to write any additional code for this if you are using built-in drivers to access your provider. Instead, you would just configure the driver and the server to use this, and your application would have to reside on the same server as your SQL provider.
The ODBC drivers available for windows support shared memory for SQL activities. To write code for these from C, you would use the ODBC API to communicate with your provider. Here's a link with a function reference.
ODBC Function Summary # MSDN
Also note that there is support for BLOBs for all SQL providers that can handle arbitrary binary data. A list of the types known to ODBC API is available here. There's no strict requirement that your statement results must be expressible in tabular form.
SQL Data Types # MSDN
On the other hand, if are concerned about communicating with internal SQL entities on your own terms, you might be able to patch something together via extensions to the SQL service you are using. For example, MS SQL Server allows extensions via Ole Automation Procedures or CLR (.net) Integration (available in MS SQL Server). You could potentially use these make something to communicate out-of-band. However, neither of these is easily created with a pure C solution.
Ole Automation Procedures in SQL Server # MSDN
CLR Integration in SQL Server # MSDN
However, I recommend that you avoid doing this, as you will find that you're at the mercy of the environment of the host service and you may not be able to participate in transactions.
If your dataset size requirements are so large that you consider RAM and direct access your best option, your needs would probably be better fulfilled by communicating only the parts that change in the dataset held outside of SQL. In addition, as a shared-memory solution is restricted to one machine, you would probably want to consider splitting the work on your dataset across multiple machines. It is more likely that you would see a performance/productivity improvement by such means than by changing how you reference data in SQL.
Last, it is tough to dictate to a SQL provider that it should avoid using filesystem storage. For MS SQL Server, one possible option is to force tempdb to reside in RAM. Here's a KB article with more details. Other DBMSs may have similar configuration options.
INF: When to use tempdb in RAM
However, the use of disk storage isn't necessarily a cause for concern. I'm unable to find a good example of how SQL providers manage a RAM / Filesystem balance, but one good analogue for SQL server is how windows is affected by page-file use. Here's a great link that details how windows behaves at high limits of operation, and how memory use doesn't necessarily correspond into overflow to disk use. Also note that applications written to run on windows are also adversely affected when the host's operation approaches these limits.
Pushing the Limits of Windows: Virtual Memory # TechNet
The DBMS would have to be designed to work as you want. Regular DBMS have their own mechanisms for managing data, and while you might be able to communicate with them via shared memory, it is more likely that you won't. The DBMS might hold most of its working data in memory; it depends on the DBMS. Typically, the data will be backed by disk storage.
What you can't do is take an arbitrary DBMS and decree to it that it shall communicate with your process via shared memory. If it is designed to do so, then you can; otherwise, you can't.
Typically, though, you use an ODBC or similar driver to access the DBMS from your application, and those who implement the driver (and the DBMS) dictate how the interprocess communication will occur.
The dev tools for SQL in Visual Studio are great.
Is it possible to develop an app for Microsoft SQL Server, and then deploy a MySQL-compatible database instead?
The dev tools for Microsoft SQL Server are really nice (i.e. LINQ support), but a MySQL-compatible column database has better performance for huge datasets.
You would need to use MySql .net connector
http://dev.mysql.com/doc/refman/5.1/en/connector-net.html
With this, you get some of the functionality that you have with SQL server (entity framework, designer, etc) there are still a bunch of things that are not supported, but it's a good start
It's possible, but a number of specifics might tend to prevent a full implementation on SQL Server, particularly with respect to stored procedures.
However, if the intent is to build a scaffolding on VisStudio and finish the development using the MySQL tools, it would work okay. You'll have to learn both SQLs quite thoroughly. The sooner you do that, the less grief there will be in the conversion.
One method for doing this would be to abstract away the database itself. That be done at least a couple of ways; the first way, you could use classes to build the SQL that your application requires, and then just use that; then all that has to happen is that it has to know how to generate the right SQL for the right server. One of the drawbacks of doing it that way, though, is that if you depend on functionality that exists on only one DBMS, you'll have to emulate it in that abstraction layer.
The other method that you could use is to create two versions of your classes that talk to the RDBMS, one for MySQL and one for Microsoft's SQL Server. Use an interface and derive from it in order to do the actual implementation. Of course, you'll want to make sure that the only responsibility of the class is to interact with the database, so if you're doing this for business layer objects, you'll be implementing those sorts of things with two classes: a low-level one for the database API, and a high-level one for actually providing the API that your application is going to consume.
Perhaps not a direct answer to your question, but the dblinq project may be of use to you.
It may be worth a look just to see the MySQL implementations within the project in order to determine what the real differences between SQL Server and MySQL are going to be and how they're going to affect you. The more you can abstract out those differences behind a dependency implementation, the easier it'll be to swap out one implementation for another.
You can write your code for SQL Server and then switch to Devart LinqConnect.
For example, you can create a LINQ to SQL model using Entity Developer (in VS integration mode or in standalone mode), then change the connection to the MySQL-specific one and run Update Database from Model wizard (don't forget to select the Regenerate Storage check box).
As a result, you will obtain a MySQL database, having structure identical to the SQL Server one.
is there a windows xp utility to make a database such that its support by sql server, oracle, and other db management systems.
the database schema is very huge so i would like to know what to use to make it so its protable from sql server to oracle if future demands that change?
In short, what you seek is nearly impossible to do successfully. Every database product has enough quirks that building such database would not perform well and would be too limiting in terms of the features you were able to use. I.e, you have to play the game of lowest common denominator with respect to features that all products implement you want to support. A far better solution is to abstract the data layer into its own library accessed via interfaces so that you can swap out your data layer. ORMs, as Rafael E. Belliard suggested, makes this simpler but it can also be done manually.
I would recommend building your database using an ORM like Hibernate for Java (or NHibernate for .NET). This would allow you to seamlessly transition from one database type to the other with little to no issues. They would allow you to logically create the database schema without a specific database in mind, which you could then move from one database to the other.
I have created applications which change from SQL Server to MySQL to Oracle to MS Access to SQLite easily (clients love that flexibility).
However, you would need to know your way around programming...