sql - Is there a way to specify table name as a string?

Question

Let us say I have a query like this:

SELECT * FROM 
(
  SELECT * FROM 
  (
    SELECT * FROM DB.dbo.Table
  )
  INNER JOIN DB.dbo.Table ON ...

I am running this query multiple times with different tables by manually changing the string everywhere. I tried declaring the following:

DECLARE @tablename AS VARCHAR(255)
SET @tablename = 'DB.dbo.Table'

But this does not seem to work as it throws me an error saying that I need to declare @tablename as a table variable before I can use it. How do I templatize my table name and if that is possible, will Intellisense still work?

Answer 1

You can wrap it in an EXEC statement like this:

declare @my_tablename nvarchar(100) = 'mytable';
exec('
SELECT * FROM 
(
  SELECT * FROM 
  (
    SELECT * FROM ' + @my_tablename + '
  )
  INNER JOIN ' + @my_tablename + ' ON ...'
);

But no, intellisense will not work in that scenario.

If you know what your output will look like in advance, then you can declare a temp table to hold the results, and then you can access that without EXEC. You will have intellisense on the temp table.

For example:

  --this must match whatever your SELECT is going to return
  CREATE TABLE #results(
    FIELD1 INT
   ,FIELD2 NVARCHAR(100)
   ,FIELD3 BIT
   );

EXEC('
  INSERT INTO #results(field1,field2,field3)
  SELECT FIELD1,FIELD2,FIELD3 FROM ' + @my_tablename
);

select * from #results  --you will have intellisense on #results