How to use variable with use statement

Posted on 2009-05-08
Last Modified: 2012-05-06

I have a script that I'm working on that uses a variable referencing the
database name (@DBName).  When I try to use this in the form of  "USE
@DBName", it doesn't work.  If I use an nvarchar datatype and create a
string (like the following);

DECLARE @SQL nvarchar(2000)
DECLARE @DBName nvarchar(200)

SET @DBName='TestDatabase'

SET @SQL = 'USE ' + @DBName
EXEC sp_sqlexec @SQL

The script runs, but the script remains focused on the master.

Is there any way to specify USE with a variable?

Question by:RIVAGHI
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LVL 75

Assisted Solution

by:Aneesh Retnakaran
Aneesh Retnakaran earned 100 total points
ID: 24341797
the dynamic sql has a different scope, and the scope come back to the current db; so whatever you need to accomplish to be done on  the other db, you should put those script inside that @sql variable and run it
LVL 31

Accepted Solution

RiteshShah earned 120 total points
ID: 24341927
you can't change focus but yes, you can do your task as Aneesh said, have a look at following script.
 though you are in MASTER database but can get results of Adventureworks database.

DECLARE @SQL nvarchar(2000)
DECLARE @DBName nvarchar(200)
SET @SQL = 'USE ' + @DBName + ';'
EXEC sp_sqlexec @SQL

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LVL 41

Assisted Solution

Sharath earned 120 total points
ID: 24342058
In Ritesh code, you can try like this. Slightly modified his code for your requirement.

DECLARE @SQL nvarchar(2000)
DECLARE @DBName nvarchar(200)
SET @DBName='AdventureWorks'
SET @SQL = 'USE ' + @DBName + ' SELECT * FROM SYS.Objects'
EXEC sp_sqlexec @SQL
You can also try with three part name.

DECLARE @SQL nvarchar(2000)
DECLARE @DBName nvarchar(200)
SET @DBName='AdventureWorks'
SET @SQL = ' SELECT * FROM + @DBName + '.SYS.Objects'
EXEC sp_sqlexec @SQL
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LVL 42

Assisted Solution

pcelba earned 100 total points
ID: 24343280
All the above written by Sharath is correct. If you really need to swith the database then you have to do it explicitly. Let suppose your database count is not infinite, so the only solution is:

DECLARE @DBName nvarchar(200)
SET @DBName='YourDatabase'
IF @DBName = 'Master'
   USE Master
ELSE IF @DBName = 'Model'
   USE Model
ELSE IF @DBName = 'YourDatabase'
   USE YourDatabase
   PRINT "Invalid Database name"
-- Remember the USE statement is not allowed in stored procedures, functions, and triggers

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LVL 75

Assisted Solution

by:Anthony Perkins
Anthony Perkins earned 60 total points
ID: 24344001
You can also preface all objects with the database name and owner, that way you do not have to change databases.  This also means you would have to enable cross database ownership chaining.

Author Comment

ID: 24404500
Thank you all !!

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