T-SQL deletion of rows not working [duplicate]

Question

This question already has answers here:

A table name as a variable (10 answers)

Closed 8 years ago.

I am using T-SQL to fetch some table names which satisfy a certain criteria - put the name of those tables in a temporary table - @MyTempTable and plan to delete all rows from all tables which have an entry in @MyTempTable.

I notice that my @MyTempTable is populated correctly with the names of the relevant tables that have to be deleted, but when I try to execute the DELETE command on each entry in @MyTempTable, it throws a syntax error saying "Must declare a table variable "@localVar". I guess this is because it is not letting me use the value of each row as the name of the table to delete entries from. Can you suggest how I can fix this?

/* Define temporary table */
DECLARE @MyTmpTable TABLE ( my_row varchar(20));

/* local variable holds the name of the table that has to be deleted based on the query below */
DECLARE @localVar varchar(20);

/* Declare curser */
DECLARE c5 CURSOR FOR (

    /* SELECT TOP 10 vc_merchant_name FROM dbo.merchant_versioned */
    select 
        t.name
    from 
        sys.tables t
    where 
        exists (
            select null from sys.columns c 
            where c.object_id = t.object_id and c.name = 'i_version_id')
);
OPEN c5;

FETCH NEXT FROM c5 INTO @localVar;
WHILE @@FETCH_STATUS = 0
BEGIN
    /*************************************************/
    DELETE FROM @localVar; /* <<<--- THIS DOESN"T WORK
    /*************************************************/
    FETCH NEXT FROM c5 INTO @localVar;
END

CLOSE c5;
DEALLOCATE c5;

Answer 1

You are getting that error because you are literally trying to execute

DELETE FROM @localVar

It's not just plugging in the value of that parameter like you want it to. You'll need to use dynamic SQL to accomplish this, and then as Rob said, use SP_EXECUTE.

DECLARE @localVar varchar(20);
DECLARE @qString varchar(max)
....
BEGIN
   set qString = 'DELETE FROM ' + @localVar
   SP_EXECUTE(qString)
END
...