Customizable database names and TempDB - sql

I have a lump of SQL that looks a little like this
IF NOT EXISTS (SELECT * FROM sys.databases WHERE name = '{FOO}')
BEGIN
EXECUTE ('CREATE DATABASE {FOO}')
ALTER DATABASE {FOO} SET AUTO_CLOSE OFF
END
{FOO} is replaced at runtime with the name of a user configurable database. The logic is that I don't want to create the database if it already exists.
If {FOO} is tempdb then I get a failure when the query runs
Option 'AUTO_CLOSE' cannot be set in database 'tempdb'.
My question is why do I get this failure? SELECT * FROM sys.databases WHERE name = 'tempdb' returns zero results so surely my whole BEGIN/END pair shouldn't run? Indeed, if I put a print statement between begin and end, I don't see any output.
My guess is that SQL Server is doing some kind of linting on the SQL to make sure I don't muck around with tempdb? I have solved the problem by using EXECUTE instead, but I'm a little confused why I have to!

Try ensuring both commands are separate and within dynamic SQL, then the change to tempdb won't be caught by the parser:
EXEC sp_executesql N'CREATE DATABASE {FOO};';
EXEC sp_executesql N'ALTER DATABASE {FOO} SET AUTO_CLOSE OFF;';
This is similar to the reason you can't do this:
IF 1 = 1
BEGIN
CREATE TABLE #t1(id INT);
END
ELSE
BEGIN
CREATE TABLE #t1(x NVARCHAR(255));
END
Even though you and I know that only one of those #t1 code paths will ever be reached, SQL Server presumes that both paths could be reached at runtime, and so complains at parse time.

Related

How to use OPENROWSET to execute a stored procedure with parameters and insert result into a temp table

I want to insert the results of a stored procedure into a temp table using OPENROWSET. However, the issue I run into is I'm not able to pass parameters to my stored procedure.
This is my stored procedure:
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
ALTER PROCEDURE [dbo].[N_spRetrieveStatement]
#PeopleCodeId nvarchar(10),
#StatementNumber int
AS
SET NOCOUNT ON
DECLARE #PersonId int
SELECT #PersonId = [dbo].[fnGetPersonId](#PeopleCodeId)
SELECT *
INTO #tempSpRetrieveStatement
FROM OPENROWSET('SQLNCLI', 'Server=PCPRODDB01;Trusted_Connection=yes;',
'EXEC Campus.dbo.spRetrieveStatement #StatementNumber, #PersonId');
--2577, 15084
SELECT *
FROM #tempSpRetrieveStatement;
OpenRowSet will not allow you to execute Procedure with input parameters. You have to use INSERT/EXEC.
INTO #tempSpRetrieveStatement(Col1, Col2,...)
EXEC PCPRODDB01.Campus.dbo.spRetrieveStatement #StatementNumber, #PersonId
Create and test a LinkedServer for PCPRODDB01 before running the above command.
The root of your problem is that you don't actually have parameters inside your statement that you're transmitting to the remote server you're connecting to, given the code sample you provided. Even if it was the very same machine you were connecting to, they'd be in different processes, and the other process doesn't have access to your session variables.
LinkedServer was mentioned as an option, and my understanding is that's the preferred option. However in practice that's not always available due to local quirks in tech or organizational constraints. It happens.
But there is a way to do this.
It's hiding in plain sight.
You need to pass literals into the string that will be executed on the other server, right?
So, you start by building the string that will do that.
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
ALTER PROCEDURE [dbo].[N_spRetrieveStatement]
#PeopleCodeId nvarchar(10),
#StatementNumber int
AS
SET NOCOUNT ON
DECLARE
#PersonId INT,
#TempSQL VARCHAR(4000) = '';
SELECT #PersonId = [dbo].[fnGetPersonId](#PeopleCodeId);
SET #TempSQL =
'EXEC Campus.dbo.spRetrieveStatement(''''' +
FORMAT(#StatementNumber,'D') +''''', ''''' +
FORMAT(#PersonId,'D') + ''''')';
--2577, 15084
Note the seemingly excessive number of quotes. That's not a mistake -- that's foreshadowing. Because, yes, OPENROWSET hates taking variables as parameters. It, too, only wants literals. So, how do we give OPENROWSET what it needs?
We create a string that is the entire statement, no variables of any kind. And we execute that.
SET #TempSQL =
'SELECT * INTO #tempSpRetrieveStatement ' +
'FROM OPENROWSET(''SQLNCLI'', ''Server=PCPRODDB01;Trusted_Connection=yes;'', ' + #TempSQL +
'EXEC Campus.dbo.spRetrieveStatement #StatementNumber, #PersonId';
EXEC (#TempSQL);
SELECT *
FROM #tempSpRetrieveStatement;
And that's it! Pretty simple except for counting your escaped quotes, right?
Now... This is almost beyond the scope of the question you asked, but it is a 'gotcha' I've experienced in executing stored procedures in another machine via OPENROWSET. You're obviously used to using temp tables. This will fail if the stored procedure you're calling is creating temp tables or doing a few other things that -- in a nutshell -- inspire the terror of ambiguity into your SQL server. It doesn't like ambiguity. If that's the case, you'll see a message like this:
"Msg 11514, Level 16, State 1, Procedure sp_describe_first_result_set, Line 1
The metadata could not be determined because statement '…your remote EXEC statement here…' in procedure '…name of your local stored procedure here…' contains dynamic SQL. Consider using the WITH RESULT SETS clause to explicitly describe the result set."
So, what's up with that?
You don't just get data back with OPENROWSET. The local and remote servers have a short conversation about what exactly the local server is going to expect from the remote server (so it can optimize receiving and processing it as it comes in -- something that's extremely important for large rowsets). Starting with SQL Server 2012, sp_describe_first_result_set is the newer procedure for this, and normally it executes quickly without you noticing it. It's just that it's powers of divination aren't unlimited. Namely, it doesn't know how to get the type and name information regarding temp tables (and probably a few other things it can't do -- PIVOT in a select statement is probably right out).
I specifically wanted to be sure to point this out because of your reply regarding your hesitation about using LinkedServer. In fact, the very same reasons you're hesitant are likely to render that error message's suggestion completely useless -- you can't even predict what columns you're getting and in what order until you've got them.
I think what you're doing will work if, say, you're just branching upstream based on conditional statements and are executing one of several potential SELECT statements. I think it will work if you're just not confident that you can depend on the upstream component being fixed and are trying to ensure that even if it varies, this procedure doesn't have to because it's very generic.
But on the other hand you're facing a situation in which you literally cannot guarantee that SQL Server can predict the columns, you're likely going to have to force some changes in the stored procedure you're calling to insist that it's stable. You might, for instance work out how to ensure all possible fields are always present by using CASE expressions rather than any PIVOT. You might create a session table that's dedicated to housing what you need to SELECT just long enough to do that then DELETE the contents back out of there. You might change the way in which you transmit your data such that it's basically gone through the equivalent of UNPIVOT. And after all that extra work, maybe it'll be just a matter of preference if you use LinkedServer or OPENROWSET to port the data across.
So that's the answer to the literal question you asked, and one of the limits on what you can do with the answer.

Stored procedure with multiple 'INSERT INTO Table_Variable EXECUTE stored_procedure' statements [duplicate]

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"

stored procedure receiving DB name to work with

I am looking to write a stored procedure which received a database name along with other parameters, and the stored procedure needs to work on the Database which it received
any thoughts please
Something like the following should work, as long as correct permissions are setup:
CREATE PROCEDURE dbo.sptest
#DB VARCHAR(50)
AS
BEGIN
DECLARE #sqlstmt VARCHAR(MAX)
SET #sqlstmt='SELECT TOP 10 * FROM ' + #DB + '.dbo.YourTableName'
sp_executesql #sqlstmt
END
GO
As mentioned, be very careful when using dynamic SQL like this- only use with trusted sources because of the ability to wreck havoc on your DB. At a minimum, you should add some checking of the value of #DB passed in to make sure it matches a limited list of database names that it will work with.

Copy trigger from one database to another

Is it possible, in a script executed in MS SQL Server 2005, to copy a trigger from one database to another?
I've been asked to write a test script for a trigger my project is using. Our test structure is to create an empty database containing only the object under test, then execute a script on that database that creates all the other objects needed for the test, fills them, runs whatever tests are needed, compares the results against expected results, and then drops everything except the object under test.
I can't just create a database that is empty except for the trigger, because the trigger depends on several tables. My test script currently runs the CREATE TRIGGER after all the required tables are created, but this won't do because the test script isn't allowed to contain the object under test.
What's been suggested is that, instead of running a CREATE TRIGGER, I somehow copy the trigger at that point in the script from the live database to the test database. I've had a quick Google and haven't found a way to do this. Thus my question - is this even possible, and if so, how can I do it?
You could read the text of the trigger with sp_helptext (triggername)
Or you can select the text into a variable and execute that:
declare #sql varchar(8000)
select #sql = object_definition(object_id)
from sys.triggers
where name = 'testtrigger'
EXEC #sql
I have a stored procedure that copies a bunch of tables to a test database. To make it less prone to mistakes that could potentially change the wrong database, I want to avoid using USE and instead explicitly specify per statement which database the trigger is copied from and to.
With the help of this answer, I came up with this solution:
DECLARE #sql NVARCHAR(MAX);
EXEC SourceDB.sys.sp_executesql
N'SELECT #output = (SELECT OBJECT_DEFINITION(OBJECT_ID(''TriggerName'')))',
N'#output VARCHAR(MAX) OUTPUT',
#output = #sql OUTPUT;
EXEC DestDB.sys.sp_executesql #sql;

Why does a T-SQL block give an error even if it shouldn't even be executed?

I was writing a (seemingly) straight-forward SQL snippet that drops a column after it makes sure the column exists.
The problem: if the column does NOT exist, the code inside the IF clause complains that it can't find the column! Well, doh, that's why it's inside the IF clause!
So my question is, why does a piece of code that shouldn't be executed give errors?
Here's the snippet:
IF exists (select * from syscolumns
WHERE id=object_id('Table_MD') and name='timeout')
BEGIN
ALTER TABLE [dbo].[Table_MD]
DROP COLUMN timeout
END
GO
...and here's the error:
Error executing SQL script [...]. Invalid column name 'timeout'
I'm using Microsoft SQL Server 2005 Express Edition.
IF exists (select * from syscolumns
WHERE id=object_id('Table_MD') and name='timeout')
BEGIN
DECLARE #SQL nvarchar(1000)
SET #SQL = N'ALTER TABLE [dbo].[Table_MD] DROP COLUMN timeout'
EXEC sp_executesql #SQL
END
GO
Reason:
When Sql server compiles the code, they check it for used objects ( if they exists ). This check procedure ignores any "IF", "WHILE", etc... constructs and simply check all used objects in code.
It may never be executed, but it's parsed for validity by Sql Server. The only way to "get around" this is to construct a block of dynamic sql and then selectively execute it
Here's how I got it to work:
Inside the IF clause, I changed the ALTER ... DROP ... command with exec ('ALTER ... DROP ...')
It seems the SQL server does a validity check on the code when parsing it, and sees that a non-existing column gets referenced somewhere (even if that piece of code will never be executed).
Using the exec(ute) command wraps the problematic code in a string, the parser doesn't complain, and the code only gets executed when necessary.
Here's the modified snippet:
IF exists (select * from syscolumns
WHERE id=object_id('Table_MD') and name='timeout')
BEGIN
exec ('ALTER TABLE [dbo].[Table_MD] DROP COLUMN timeout')
END
GO
By the way, there is a similar issue in Oracle, and a similar workaround using the "execute immediate" clause.