How to use T-SQL to call exec(@sql) to change current database? [duplicate]

This question already has answers here: Closed 10 years ago.

Possible Duplicate:

In SQL server is there any way to get the 'use database' command to accept a variable

We can change the database by their name is no problem as below

USE master
GO

But I need this in a script and have the database name in a variable. How to make this?

select @cmd = N'u开发者_Go百科se ' + @oldDb  + N';'
exec sp_executesql @cmd

That doesn't work - the current database stays the same after the execution.

Is something possible at all?

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Apparently the problem is with using GO within a dynamic sql statement, because execute sql doesn't support multiple batches. Please see this link for the solution. Change Database with Dynamic SQL

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Perhaps there's a valid reason for this, but if possible I would recommend naming the DB by name in your script where required. for example

databasename.table.owner.field