I have a Query requiring Varchar to be converted into INT. Iam not currently posting the query itself as I do not believe the problem to be there.
I setup the query on my home PC using a backup from the servers SQL file. I have Server 2008 R2 installed on both machines.
The Query runs 100% on my PC but gives an error converting varchar to INT when run on the server.
Iam guessing there is a setting somewhere that is not the same? I have checked Regional settings and the problem is not there. any ideas?
The problem lies in how the query is evaluated. You have no guarantee or what order parts of the query will be evaluated in, so on one machine a filter may happen after a convert, on another it could do. Or the WHERE clause conditions can be evaluated in a different order
SQL is declarative, not procedural. With SQL you ask for what you want and the query optimiser honours that how it sees fit. In a procedural language (C#, Java etc) you'd control the execution order.
The reason is full described here: Why use Select Top 100 Percent?
Related
I have a server called ERP-SERVER, and a server called SQLDEV-SERVER.
They both have a blob instance, but we never copy over the complete blob to the SQLDEV-SERVER as that would be too much data.
So when trying to access a file on our test server, it should first check if that file exists on the SQLDEV-SERVER, and if not check if the file exists on the ERP-SERVER. This is where it goes wrong. This piece of code (SQL) used to work but somewhere along the way it broke. I have narrowed it down to the inter database query just returning completely different results.
so for instance i run this query on the ERP-SERVER instance in SQL management studio:
SELECT count(*)
FROM [erp-server].[Extranet_Blob].[dbo].[FileStorBlob]
this returns 223221 results.
When i run the same query on the SQLDEV-SERVER instance in SQL management studio, it returns 313 results.
It points to the same server and same database, yet a completely different count, which is why it is also not returning the files from the live environment when it is not found on the dev environment.
Any pointers as to where this problem could be situated?
Look very carefully at your linked server definition. When you are running the query on SQLDEV-SERVER it is using the linked server definition of that name rather than necessarily the ERP_Server. Is it possible that someone has fiddled with the definition?
I have a MS Access query that is based on a linked ODBC table (Oracle).
I'm troubleshooting the poor performance of the query here: Access not properly translating TOP predicate to ODBC/Oracle SQL.
SELECT ri.*
FROM user1_road_insp AS ri
WHERE ri.insp_id = (
select
top 1 ri2.insp_id
from
user1_road_insp ri2
where
ri2.road_id = ri.road_id
and year(insp_date) between [Enter a START year:] and [Enter a END year:]
order by
ri2.insp_date desc,
ri2.length desc,
ri2.insp_id
);
The documentation says:
When you spot a problem, you can try to resolve it by changing the local query. This is often difficult to do successfully, but you may
be able to add criteria that are sent to the server, reducing the
number of rows retrieved for local processing.
In many cases you will find that, despite your best efforts, Office Access still retrieves some entire tables unnecessarily and
performs final query processing locally.
However, it's occurred to me that I don't really understand what sort of SQL I should be writing to make both Access and ODBC/Oracle happy.
Should I be writing some sort of generic SQL that Access can understand in a local query AND that can be easily translated to ODBC/Oracle SQL? Is generic SQL a real thing?
What kind of SQL does the ODBC driver use? It depends as typically MS Access has three types of external data connections that interfaces with different SQL dialects each with the ODBC API.
Linked tables that acts like local tables but are ODBC connected data sources and not stored locally. Once they are incorporated in an Access app, these tables can only use MS Access' SQL dialect. They can be joined with local or even other backend tables from other sources.
Hence, why TOP is available in MS Access and not Oracle. You are essentially using Access SQL to manipulate Oracle data. ODBC serves as the origin point of data while Access' Jet/ACE SQL engine does the processing and resultset viewing in cached memory.
Pass-through queries that do not see local tables or anything else in local app's environment. Such queries use the SQL dialect of the connected database here being Oracle.
Hence, why TOP is NOT available in Oracle and double quotes are allowed in column identifiers. Such quoting would fail in MS Access. Essentially, you are using Oracle SQL to manipulate Oracle data in an Access app. You can take the output of the sqlout.txt log and run it in a pass-through query ODBC-connected to your Oracle database.
ADO/DAO Recordsets that are run entirely via code such as VBA and are direct connections to data sources and uses the connecting database's dialect.
Here, you using Oracle SQL to manipulate Oracle data in an Access app via the ODBC API.
In each one of these types, you will have to connect to a backend ODBC data source. You do not even need to use the GUI but can use Access' object library to create linked tables (see DoCmd.TransferDatabase) and pass through querydefs (see QueryDef.Connect or .Execute).
I suspect the sqlout.txt log you see are translations of the ODBC calls to its native dialect.
To build on #Parfait's point #1:
From Microsoft Access Developer's Guide to SQL Server by Mary Chipman and Andy Baron:
Optimizing Access Queries:
There's a common misconception that the Jet engine always retrieves all the data in linked SQL Server tables and then processes the data locally. This is not usually true. Jet is perfectly capable of sending efficient queries to SQL Server over ODBC and retrieving only the rows required. However, in some cases, Jet will in fact be forced to fetch all the data in certain tables first and then process it. You should be aware of when you are forcing Jet to do this and be sure that it is justified. The following are some general guidelines to follow when creating your Access queries:
Using expressions that can't be evaluated by the server will cause Jet to retrieve all the data required to evaluate those expressions locally. The impact of using Access-specific expressions, such as domain aggregate functions, Access financial functions, or custom VBA functions will vary depending on where in your query the expressions are used. Using such an expression in the SELECT clause will usually not cause a problem because no extra data will be returned. However, if the expression is in the WHERE clause, that criterion cannot be applied on the server, and all the data evaluated by the expression will have to be returned.
With multiple criteria, as many as possible will be processed on the server. This means that even if you use criteria that you know include functions that will need to be processed by Jet, adding other criteria that can be handled by the server will reduce the number of records that Jet has to process. Adding criteria on indexed columns is especially helpful.
Query syntax that includes an Access-specific extension to SQL, not supported by the ODBC driver, may force processing to be done on the client by Access. For example, even though SELECT TOP 5 PERCENT is now supported by SQL Server, it is not supported by the ODBC driver. If you use that syntax in an Access query, Jet will need to retrieve all the records and calculate which ones are in the top 5 percent. On the other hand, even though crosstab queries are specific to Access, Jet will translate them into simple GROUP BY queries and fetch just the required data in one trip to the server unless problematic criteria is used.
Heterogeneous joins between local and remote tables or between remote tables that are in different data sources will, of course, have to be processed by Jet after the source data is retrieved. However, if the remote join field is indexed and the table is large, Jet will often use the index to retrieve only the required rows by making multiple calls to the remote table, one fore each row required.
Jet allows you to mix data types within [typo - fix later] of UNION queries and within expressions, but SQL server doesn't. Such mixing of data types will force processing to be done locally.
Multiple outer joins in one query will be processed locally.
The most important factor is reducing the total number of records being fetched. Jet will retrieve multiple batches of records in the background until the result set is complete, so even though you may seem to get results back immediately, a continuing load is being placed on the server for large result sets.
Note: this book is quite old (published in 2000) and is in reference to Jet Engine. I imagine things might be slightly different in newer versions of Access which use ACE, although I don't have a source to back this up.
I have had an odd error I cannot explain. Basically, I am running a query to my SQL database using excel and am having non-existent data pop up when it comes to a very particular order in my database.
Here is a simple query surrounding this order:
select * from OR200100 where OR200100.OR20001='0000793605'
Here is the output in EXCEL
And here is the same output in SQL
what is happening here? How could the same query generate 2 different results?
Run SQL Server Profiler against the database if you can, then compare the output to the sql query that you are running in ssms.
OK, so it's SQL Server then, that's important because different SQL products can have very different idiosyncrasies and controls.
The next things to check are these:
Is OR200100 a Table or a View? If it's a view then post it's code.
Are you using the same Login/account from both Excel and SSMS?
Are you sure that you are connecting to the same Server and Database? SSMS tells you what you are connected to, but client apps like Excel do not and it is very common for this type of problem to be caused by the app connecting to a Dev or QA version of the database. See here for some of the different ways that this can happen:
So I had a very similar problem, my query was grouping by week numbers. What I found was that one of the queries had set datefirst 5 set whilst the other didn't. I guess the key thing here is make sure, if you are using any SET operations in your ssms queries, these are identical to those in the Excel query string.
While this may sound like a beginner 101 problem I think it is a bit more complicated.
I have two instances of SQL server, one is a log-shipped read/only standby copy of the master database that is used for reporting purposes.
They are both 64-bit SQL 2005, SP3.
The LogShipped Instance is: 9.00.4035.00 (Standard Edition)
The Original Instance is: 9.00.4035.00 (Enterprise Edition) in an Active / Passive Cluster.
Server collation is Latin1_General_CI_AI on both and they both run on Server 2003 64 bit.
I have a query that runs and executes fine on the master database server but it fails on the standby / read-only copy with a conversion of nvarchar to int.
The code is identical and i've copied and pasted it from the main instance query window just to double check.
Is there a bug in SQL server somewhere? I can paste the query if needed (its a bog-standard select with some in-line tables)
Just don't understand why it works on the one yet the log-shipped copy fails.
Any pointers is much appreciated.
-- Edit
I have found the culprit.. the transaction log database contains invalid data that isn't in the primary database.. quite why they are out of sych I do not know yet as the transaction log shipping is still working and I have no errors in the job-history.
Just a few orphaned records that are invalid that are not in the primary db.. how odd
Are you sure the data is the same?
If you try
select convert(int, char(10))
it will probably get a similar error, so your query will fail if the value you are converting is char(10), which may not be be obvious when viewing the data.
check any trigger if that is updating any view(having int for the specific column) based on your table
I've developed my website using EF4 and SQL Server 2005, but when moving to the staging site it turns out that they use SQL Server 2000.
Now I'm getting this error, which I believe is related to SQL Server 2000:
Incorrect syntax near '('. 'row_number' is not a recognized function name.
Is there a way of fixing this?
Thanks
EF v4 does not support SQL Server 2000. More details here:
https://connect.microsoft.com/VisualStudio/feedback/details/499186/entity-framework-v2-doesn-t-support-sql-2000
I came across the exact same problem and as per the comments/responses on StackOverflow I had almost given up and flicked it to client to upgrade their database to > 2000 version. Unfortunately that wasn't possible for them due to many other issues. I had to go around googling for a solution and from somewhere I found a work-around.
This is what I did.
Right clicked the ModelName.EDMX file -> Open With
Selected XML (Text) Editor
Found ProviderManifestToken="2005" and replaced it with
ProviderManifestToken="2000"
Published the changes and voila!
Now the reason I'm saying it's a work-around (not a solution) is because
If you update your model from database again and your development
machine database is >= 2000 (which is likely to be a case as SQL
2000 connection is not supported at all by MS according to this
article) this value in the XML will change automatically
Also, the queries generated by EF after this change have worked in
my situation but I cannot guarantee that all the queries ever
generated by your application would work without any problems
Row_Number() returns the sequential number for a each row returned. Are you calling Row_number(), or is the entity framework?
Either way, you may be able to write a user-defined function that re-implements ROW_NUMBER. Stackoverflow post on this here:
ROW_NUMBER Alternative for SQL Server 2000
Not sure this is going to do any good in the long run; you're likely to find that you get around this problem only to encounter the next reason that EF doesn't work on SQL 2000. But, it might be worth the few minutes to try.