I saw this question quite a many times but I couldn't get the answer that would satisfy me. Basically what people and books say is "Although temporary tables are deleted when they go out of scope, you should explicitly delete them when they are no longer needed to reduce resource requirements on the server".
It is quite clear to me that when you are working in management studio and creating tables, then until you close your window or disconnect, you will use some resources for that table and it is logically that it is better to drop them.
But when you work with procedure then if you would like to cleanup tables most probably you will do that at the really end of it (I am not talking about the situation when you drop the table as soon as you really do not need that in the procedure). So the workflow is something like that :
When you drop in SP:
Start of SP execution
Doing some stuff
Drop tables
End of execution
And as far as I understand how can it possibly work when you do not drop:
Start of SP execution
Doing some stuff
End of execution
Drop tables
What's the difference here? I can only imagine that some resources are needed to identify the temporary tables. Any other thoughts?
UPDATE:
I ran simple test with 2 SP:
create procedure test as
begin
create table #temp (a int)
insert into #temp values (1);
drop table #temp;
end
and another one without drop statements. I've enabled user statistics and ran the tests:
declare #i int = 0;
while #i < 10000
begin
exec test;
SET #i= #i + 1;
end
That's what I've got (Trial 1-3 dropping table in SP, 4-6 do not dropping)
As the picture shows that all stats are the same or decreased a bit when I do not drop temporary table.
UPDATE2:
I ran this test 2nd time but now with 100k calls and also added SET NOCOUNT ON. These are the results:
As the 2nd run confirmed that if you do not drop the table in SP then you actually save some user time as this is done by some other internal process but outside of the user time.
You can read more about in in this Paul White's article: Temporary Tables in Stored Procedures
CREATE and DROP, Don’t
I will talk about this in much more detail in my next post, but the
key point is that CREATE TABLE and DROP TABLE do not create and drop
temporary tables in a stored procedure, if the temporary object can be
cached. The temporary object is renamed to an internal form when DROP
TABLE is executed, and renamed back to the same user-visible name when
CREATE TABLE is encountered on the next execution. In addition, any
statistics that were auto-created on the temporary table are also
cached. This means that statistics from a previous execution remain
when the procedure is next called.
Technically, a locally scoped temp table (one with a single hashtag before it) will automatically drop out of scope after your SPID is closed. There are some very odd cases where you get a temp table definition cached somewhere and then no real way to remove it. Usually that happens when you have a stored procedure call which is nested and contains a temp table by the same name.
It's good habit to get into dropping your tables when you're done with them but unless something unexpected happens, they should be de-scoped anyway once the proc finishes.
I am receiving an error trying to build a macro using a stored procedure with a cursor.
Some relevant details need to be included. This is for a document in an Electronic Health Records system. First, I develop the templates/tables, then I create document macros to pull all the information into the EHR documents. I have used stored procedures hundreds of times, so I know that it is the cursor that is causing it to fail.
All I do is pass in the parameters and it creates a grid on the document. Whether or not it is a limitation of the software that is used to create the documents, I don't know. I figured I would ask here to make sure my code is correct.
Here is my table:
txt_enc_id enc_id_generate
12345 93847
12345 75430
12345 93946
I am passing in the enc_id on the document macro, which will match up to the txt_enc_id column, and I need a stored procedure to run for each of the enc_id_generate rows in that table
Here's what I have for my stored procedure:
#enc_id VARCHAR(36)
AS
BEGIN
SET NOCOUNT ON
DECLARE #enc_id_generate VARCHAR(36)
DECLARE enc_id_cursor CURSOR
FOR
(SELECT enc_id_generate
FROM my_table
WHERE txt_enc_id = #enc_id)
OPEN enc_id_cursor
FETCH NEXT FROM enc_id_cursor INTO #enc_id_generate
WHILE ##FETCH_STATUS = 0
BEGIN
-- Here is the stored procedure that needs to run for each record.
-- The only parameter it uses is #enc_id_generate
FETCH NEXT FROM enc_id_cursor INTO #enc_id_generate
END
CLOSE enc_id_cursor
DEALLOCATE enc_id_cursor
SET NOCOUNT OFF
END
When I try to create the macro, I pass in the #enc_id, click ok in the parameter window, and I am getting this error:
Failed to update the macro builder window.
Cannot find table 0.
Do I somehow need to NOT have the stored procedure inside the cursor, and somehow call it to execute? I don't know how to do that. I am not a SQL guru, so forgive me if I have murdered this code. I do know that cursors should be used sparingly, but the table holding those Encounter IDs will rarely have more than 2 or 3 records.
I hope this makes sense. Thanks in advance for any advice you may have.
Lyn
EDIT This questions is no longer valid as the issue was something else. Please see my explanation below in my answer.
I'm not sure of the etiquette so i'l leave this question in its' current state
I have a stored procedure that writes some data to a table.
I'm using Microsoft Practices Enterprise library for making my stored procedure call.
I invoke the stored procedure using a call to ExecuteNonQuery.
After ExecuteNonQuery returns i invoke a 3rd party library. It calls back to me on a separate thread in about 100 ms.
I then invoke another stored procedure to pull the data I had just written.
In about 99% of cases the data is returned. Once in a while it returns no rows( ie it can't find the data). If I put a conditional break point to detect this condition in the debugger and manually rerun the stored procedure it always returns my data.
This makes me believe the writing stored procedure is working just not committing when its called.
I'm fairly novice when it comes to sql, so its entirely possible that I'm doing something wrong. I would have thought that the writing stored procedure would block until its contents were committed to the db.
Writing Stored Procedure
ALTER PROCEDURE [dbo].[spWrite]
#guid varchar(50),
#data varchar(50)
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;
-- see if this guid has already been added to the table
DECLARE #foundGuid varchar(50);
SELECT #foundGuid = [guid] from [dbo].[Details] where [guid] = #guid;
IF #foundGuid IS NULL
-- first time we've seen this guid
INSERT INTO [dbo].[Details] ( [guid], data ) VALUES (#guid, #data)
ELSE
-- updaeting or verifying order
UPDATE [dbo].[Details] SET data =#data WHERE [guid] = #guid
END
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
Reading Stored Procedure
ALTER PROCEDURE [dbo].[spRead]
#guid varchar(50)
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;
SELECT * from [dbo].[Details] where [guid] = #guid;
END
To actually block other transactions and manually commit,
maybe adding
BEGIN TRANSACTION
--place your
--transactions you wish to do here
--if everything was okay
COMMIT TRANSACTION
--or
--ROLLBACK TRANSACTION if something went wrong
could help you?
I’m not familiar with the data access tools you mention, but from your description I would guess that either the process does not wait for the stored procedure to complete execution before proceeding to the next steps, or ye olde “something else” is messing with the data in between your write and read calls.
One way to tell what’s going on is to use SQL Profiler. Fire it up, monitor all possible query execution events on the database (including stored procedure and stored procedures line start/stop events), watch the Text and Started/Ended columns, correlate this with the times you are seeing while tracing the application, and that should help you figure out what’s going on there. (SQL Profiler can be complex to use, but there are many sources on the web that explain it, and it is well worth learning how to use it.)
I'll leave my answer below as there are comments on it...
Ok, I feel shame I had simplified my question too much. What was actually happening is two things:
1) the inserting procedure is actually running on a separate machine( distributed system).
2) the inserting procedure actually inserts data into two tables without a transaction.
This means the query can run at the same time and find the tables in a state where one has been written to and the second table hasn't' yet had its write committed.
A simple transaction fixes this as the reading query can handle either case of no write or full write but couldn't handle the case of one table written to and the other having a pending commit.
Well it turns out that when I created the stored procedure the MSSQLadmin tool added a line to it by default:
SET NOCOUNT ON;
If I turn that to:
SET NOCOUNT OFF;
then my procedure actually commits to the database properly. Strange that this default would actually end up causing problems.
Easy way using try-catch, like it if useful
BEGIN TRAN
BEGIN try
INSERT INTO meals
(
...
)
Values(...)
COMMIT TRAN
END try
BEGIN catch
ROLLBACK TRAN
SET #resp = (convert(varchar,ERROR_LINE()), ERROR_MESSAGE() )
END catch
I have three stored procedures Sp1, Sp2 and Sp3.
The first one (Sp1) will execute the second one (Sp2) and save returned data into #tempTB1 and the second one will execute the third one (Sp3) and save data into #tempTB2.
If I execute the Sp2 it will work and it will return me all my data from the Sp3, but the problem is in the Sp1, when I execute it it will display this error:
INSERT EXEC statement cannot be nested
I tried to change the place of execute Sp2 and it display me another error:
Cannot use the ROLLBACK statement
within an INSERT-EXEC statement.
This is a common issue when attempting to 'bubble' up data from a chain of stored procedures. A restriction in SQL Server is you can only have one INSERT-EXEC active at a time. I recommend looking at How to Share Data Between Stored Procedures which is a very thorough article on patterns to work around this type of problem.
For example a work around could be to turn Sp3 into a Table-valued function.
This is the only "simple" way to do this in SQL Server without some giant convoluted created function or executed sql string call, both of which are terrible solutions:
create a temp table
openrowset your stored procedure data into it
EXAMPLE:
INSERT INTO #YOUR_TEMP_TABLE
SELECT * FROM OPENROWSET ('SQLOLEDB','Server=(local);TRUSTED_CONNECTION=YES;','set fmtonly off EXEC [ServerName].dbo.[StoredProcedureName] 1,2,3')
Note: You MUST use 'set fmtonly off', AND you CANNOT add dynamic sql to this either inside the openrowset call, either for the string containing your stored procedure parameters or for the table name. Thats why you have to use a temp table rather than table variables, which would have been better, as it out performs temp table in most cases.
OK, encouraged by jimhark here is an example of the old single hash table approach: -
CREATE PROCEDURE SP3 as
BEGIN
SELECT 1, 'Data1'
UNION ALL
SELECT 2, 'Data2'
END
go
CREATE PROCEDURE SP2 as
BEGIN
if exists (select * from tempdb.dbo.sysobjects o where o.xtype in ('U') and o.id = object_id(N'tempdb..#tmp1'))
INSERT INTO #tmp1
EXEC SP3
else
EXEC SP3
END
go
CREATE PROCEDURE SP1 as
BEGIN
EXEC SP2
END
GO
/*
--I want some data back from SP3
-- Just run the SP1
EXEC SP1
*/
/*
--I want some data back from SP3 into a table to do something useful
--Try run this - get an error - can't nest Execs
if exists (select * from tempdb.dbo.sysobjects o where o.xtype in ('U') and o.id = object_id(N'tempdb..#tmp1'))
DROP TABLE #tmp1
CREATE TABLE #tmp1 (ID INT, Data VARCHAR(20))
INSERT INTO #tmp1
EXEC SP1
*/
/*
--I want some data back from SP3 into a table to do something useful
--However, if we run this single hash temp table it is in scope anyway so
--no need for the exec insert
if exists (select * from tempdb.dbo.sysobjects o where o.xtype in ('U') and o.id = object_id(N'tempdb..#tmp1'))
DROP TABLE #tmp1
CREATE TABLE #tmp1 (ID INT, Data VARCHAR(20))
EXEC SP1
SELECT * FROM #tmp1
*/
My work around for this problem has always been to use the principle that single hash temp tables are in scope to any called procs. So, I have an option switch in the proc parameters (default set to off). If this is switched on, the called proc will insert the results into the temp table created in the calling proc. I think in the past I have taken it a step further and put some code in the called proc to check if the single hash table exists in scope, if it does then insert the code, otherwise return the result set. Seems to work well - best way of passing large data sets between procs.
This trick works for me.
You don't have this problem on remote server, because on remote server, the last insert command waits for the result of previous command to execute. It's not the case on same server.
Profit that situation for a workaround.
If you have the right permission to create a Linked Server, do it.
Create the same server as linked server.
in SSMS, log into your server
go to "Server Object
Right Click on "Linked Servers", then "New Linked Server"
on the dialog, give any name of your linked server : eg: THISSERVER
server type is "Other data source"
Provider : Microsoft OLE DB Provider for SQL server
Data source: your IP, it can be also just a dot (.), because it's localhost
Go to the tab "Security" and choose the 3rd one "Be made using the login's current security context"
You can edit the server options (3rd tab) if you want
Press OK, your linked server is created
now your Sql command in the SP1 is
insert into #myTempTable
exec THISSERVER.MY_DATABASE_NAME.MY_SCHEMA.SP2
Believe me, it works even you have dynamic insert in SP2
I found a work around is to convert one of the prods into a table valued function. I realize that is not always possible, and introduces its own limitations. However, I have been able to always find at least one of the procedures a good candidate for this. I like this solution, because it doesn't introduce any "hacks" to the solution.
I encountered this issue when trying to import the results of a Stored Proc into a temp table, and that Stored Proc inserted into a temp table as part of its own operation. The issue being that SQL Server does not allow the same process to write to two different temp tables at the same time.
The accepted OPENROWSET answer works fine, but I needed to avoid using any Dynamic SQL or an external OLE provider in my process, so I went a different route.
One easy workaround I found was to change the temporary table in my stored procedure to a table variable. It works exactly the same as it did with a temp table, but no longer conflicts with my other temp table insert.
Just to head off the comment I know that a few of you are about to write, warning me off Table Variables as performance killers... All I can say to you is that in 2020 it pays dividends not to be afraid of Table Variables. If this was 2008 and my Database was hosted on a server with 16GB RAM and running off 5400RPM HDDs, I might agree with you. But it's 2020 and I have an SSD array as my primary storage and hundreds of gigs of RAM. I could load my entire company's database to a table variable and still have plenty of RAM to spare.
Table Variables are back on the menu!
I recommend to read this entire article. Below is the most relevant section of that article that addresses your question:
Rollback and Error Handling is Difficult
In my articles on Error and Transaction Handling in SQL Server, I suggest that you should always have an error handler like
BEGIN CATCH
IF ##trancount > 0 ROLLBACK TRANSACTION
EXEC error_handler_sp
RETURN 55555
END CATCH
The idea is that even if you do not start a transaction in the procedure, you should always include a ROLLBACK, because if you were not able to fulfil your contract, the transaction is not valid.
Unfortunately, this does not work well with INSERT-EXEC. If the called procedure executes a ROLLBACK statement, this happens:
Msg 3915, Level 16, State 0, Procedure SalesByStore, Line 9 Cannot use the ROLLBACK statement within an INSERT-EXEC statement.
The execution of the stored procedure is aborted. If there is no CATCH handler anywhere, the entire batch is aborted, and the transaction is rolled back. If the INSERT-EXEC is inside TRY-CATCH, that CATCH handler will fire, but the transaction is doomed, that is, you must roll it back. The net effect is that the rollback is achieved as requested, but the original error message that triggered the rollback is lost. That may seem like a small thing, but it makes troubleshooting much more difficult, because when you see this error, all you know is that something went wrong, but you don't know what.
I had the same issue and concern over duplicate code in two or more sprocs. I ended up adding an additional attribute for "mode". This allowed common code to exist inside one sproc and the mode directed flow and result set of the sproc.
what about just store the output to the static table ? Like
-- SubProcedure: subProcedureName
---------------------------------
-- Save the value
DELETE lastValue_subProcedureName
INSERT INTO lastValue_subProcedureName (Value)
SELECT #Value
-- Return the value
SELECT #Value
-- Procedure
--------------------------------------------
-- get last value of subProcedureName
SELECT Value FROM lastValue_subProcedureName
its not ideal, but its so simple and you don't need to rewrite everything.
UPDATE:
the previous solution does not work well with parallel queries (async and multiuser accessing) therefore now Iam using temp tables
-- A local temporary table created in a stored procedure is dropped automatically when the stored procedure is finished.
-- The table can be referenced by any nested stored procedures executed by the stored procedure that created the table.
-- The table cannot be referenced by the process that called the stored procedure that created the table.
IF OBJECT_ID('tempdb..#lastValue_spGetData') IS NULL
CREATE TABLE #lastValue_spGetData (Value INT)
-- trigger stored procedure with special silent parameter
EXEC dbo.spGetData 1 --silent mode parameter
nested spGetData stored procedure content
-- Save the output if temporary table exists.
IF OBJECT_ID('tempdb..#lastValue_spGetData') IS NOT NULL
BEGIN
DELETE #lastValue_spGetData
INSERT INTO #lastValue_spGetData(Value)
SELECT Col1 FROM dbo.Table1
END
-- stored procedure return
IF #silentMode = 0
SELECT Col1 FROM dbo.Table1
Declare an output cursor variable to the inner sp :
#c CURSOR VARYING OUTPUT
Then declare a cursor c to the select you want to return.
Then open the cursor.
Then set the reference:
DECLARE c CURSOR LOCAL FAST_FORWARD READ_ONLY FOR
SELECT ...
OPEN c
SET #c = c
DO NOT close or reallocate.
Now call the inner sp from the outer one supplying a cursor parameter like:
exec sp_abc a,b,c,, #cOUT OUTPUT
Once the inner sp executes, your #cOUT is ready to fetch. Loop and then close and deallocate.
If you are able to use other associated technologies such as C#, I suggest using the built in SQL command with Transaction parameter.
var sqlCommand = new SqlCommand(commandText, null, transaction);
I've created a simple Console App that demonstrates this ability which can be found here:
https://github.com/hecked12/SQL-Transaction-Using-C-Sharp
In short, C# allows you to overcome this limitation where you can inspect the output of each stored procedure and use that output however you like, for example you can feed it to another stored procedure. If the output is ok, you can commit the transaction, otherwise, you can revert the changes using rollback.
On SQL Server 2008 R2, I had a mismatch in table columns that caused the Rollback error. It went away when I fixed my sqlcmd table variable populated by the insert-exec statement to match that returned by the stored proc. It was missing org_code. In a windows cmd file, it loads result of stored procedure and selects it.
set SQLTXT= declare #resets as table (org_id nvarchar(9), org_code char(4), ^
tin(char9), old_strt_dt char(10), strt_dt char(10)); ^
insert #resets exec rsp_reset; ^
select * from #resets;
sqlcmd -U user -P pass -d database -S server -Q "%SQLTXT%" -o "OrgReport.txt"
I have a stored procedure for SQL Server 2000 that can only have a single instance being executed at any given moment. Is there any way to check and ensure that the procedure is not currently in execution?
Ideally, I'd like the code to be self contained and efficient (fast). I also don't want to do something like creating a global temp table checking for it's existence because if the procedure fails for some reason, it will always be considered as running...
I've searched, I don't think this has been asked yet. If it has been, sorry.
yes there is a way. use what is known as SQL Server Application locks.
EDIT: yes this also works in SQL Server 2000.
You can use sp_getapplock sp_releaseapplock as in the example found at Lock a Stored Procedure for Single Use Only.
But, is that what you are really trying to do? Are you trying to get a transaction with a high isolation level? You would also likely be much better off handling that type of concurrency at the application level as in general higher level languages have much better primitives for that sort of thing.
how about locking a dummy table? That wouldn't cause deadlocks in case of failures.
One of the initial external links shared in the replies had helpful info but personally I prefer for standalone answers/snippets to be right here on the Stack Overflow question page. See below snippet for what I used and solved my (similar) problem. If anyone has problems (or adjustment suggestions) please chime in.
IF EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[MyLockedAndDelayedStoredProcedure]') AND type in (N'P', N'PC'))
DROP PROCEDURE [GetSessionParticipantAnswersFromEmailAddressAndSessionName]
GO
CREATE PROCEDURE [MyLockedAndDelayedStoredProcedure]
#param1 nvarchar(max) = ''
AS
BEGIN
DECLARE #LockedTransactionReturnCode INT
PRINT 'MyLockedAndDelayedStoredProcedure CALLED at ' + CONVERT(VARCHAR(12),GETDATE(),114);
BEGIN TRANSACTION
EXEC #LockedTransactionReturnCode =sp_getapplock #Resource='MyLockedAndDelayedStoredProcedure_LOCK', #LockMode='Exclusive', #LockOwner='Transaction', #LockTimeout = 10000
PRINT 'MyLockedAndDelayedStoredProcedure STARTED at ' + CONVERT(VARCHAR(12),GETDATE(),114);
-- Do your Stored Procedure Stuff here
Select #param1;
-- If you don't want/need a delay remove this line
WAITFOR DELAY '00:00:3'; -- 3 second delay
PRINT 'MyLockedAndDelayedStoredProcedure ENDED at ' + CONVERT(VARCHAR(12),GETDATE(),114);
COMMIT
END
-- https://gist.github.com/cemerson/366358cafc60bc1676f8345fe3626a3f
At the start of the procedure check if piece of data is 'locked' if not lock it
At end of procedure unlock the piece of data.
ie
SELECT #IsLocked=IsLocked FROM CheckLockedTable Where spName = 'this_storedProcedure'
IF #IsLocked = 1
RETURN
ELSE
UPDATE CheckLockedTable SET IsLocked = 1 Where spName = 'this_storedProcedure'
.
.
.
-- At end of Stored Procedure
UPDATE CheckLockedTable SET IsLocked = 0 Where spName = 'this_storedProcedure'