sql use statement with variable

Question

I\'m trying to switch the current database with a SQL statement. I have tried the following, but all attempts failed:

1. USE @DatabaseName
2. EXEC sp_sqlexe

Answer 1

The problem with the former is that what you're doing is USE 'myDB' rather than USE myDB. you're passing a string; but USE is looking for an explicit reference.

The latter example works for me.

declare @sql varchar(20)
select @sql = 'USE myDb'
EXEC sp_sqlexec @Sql

-- also works
select @sql = 'USE [myDb]'
EXEC sp_sqlexec @Sql

Answer 2

try this:

DECLARE @Query         varchar(1000)
DECLARE @DatabaseName  varchar(500)

SET @DatabaseName='xyz'
SET @Query='SELECT * FROM Server.'+@DatabaseName+'.Owner.Table1'
EXEC (@Query)

SET @DatabaseName='abc'
SET @Query='SELECT * FROM Server.'+@DatabaseName+'.Owner.Table2'
EXEC (@Query)

Answer 3

Use exec sp_execsql @Sql

Example

DECLARE @sql as nvarchar(100)  
DECLARE @paraDOB datetime  
SET @paraDOB = '1/1/1981'  
SET @sql=N'SELECT * FROM EmpMast WHERE DOB >= @paraDOB'  
exec sp_executesql @sql,N'@paraDOB datetime',@paraDOB

Answer 4

I case that someone need a solution for this, this is one:

if you use a dynamic USE statement all your query need to be dynamic, because it need to be everything in the same context.

You can try with SYNONYM, is basically an ALIAS to a specific Table, this SYNONYM is inserted into the sys.synonyms table so you have access to it from any context

Look this static statement:

CREATE SYNONYM MASTER_SCHEMACOLUMNS FOR Master.INFORMATION_SCHEMA.COLUMNS
SELECT * FROM MASTER_SCHEMACOLUMNS

Now dynamic:

DECLARE @SQL VARCHAR(200)
DECLARE @CATALOG VARCHAR(200) = 'Master'

IF EXISTS(SELECT * FROM  sys.synonyms s WHERE s.name = 'CURRENT_SCHEMACOLUMNS')
BEGIN
DROP SYNONYM CURRENT_SCHEMACOLUMNS
END

SELECT @SQL = 'CREATE SYNONYM CURRENT_SCHEMACOLUMNS FOR '+ @CATALOG +'.INFORMATION_SCHEMA.COLUMNS';
EXEC sp_sqlexec @SQL

--Your not dynamic Code
SELECT * FROM CURRENT_SCHEMACOLUMNS

Now just change the value of @CATALOG and you will be able to list the same table but from different catalog.

Answer 5

Just wanted to thank KM for his valuable solution. I implemented it myself to reduce the amount of lines in a shrinkdatabase request on SQLServer. Here is my SQL request if it can help anyone :

-- Declare the variable to be used
DECLARE @Query varchar (1000)
DECLARE @MyDBN varchar(11);
-- Initializing the @MyDBN variable (possible values : db1, db2, db3, ...)
SET @MyDBN = 'db1';
-- Creating the request to execute
SET @Query='use '+ @MyDBN +'; ALTER DATABASE '+ @MyDBN +' SET RECOVERY SIMPLE WITH NO_WAIT; DBCC SHRINKDATABASE ('+ @MyDBN +', 1, TRUNCATEONLY); ALTER DATABASE '+ @MyDBN +' SET RECOVERY FULL WITH NO_WAIT'
-- 
EXEC (@Query)

Answer 6

If SQLCMD is an option, it supports scripting variables above and beyond what straight T-SQL can do. For example: http://msdn.microsoft.com/en-us/library/ms188714.aspx