T-SQL If Else condition on the same Temp Table - sql

Question

Here is what I am trying to do:
IF len(Variable) > 1
BEGIN
SELECT * INTO #TEMPTAB FROM multiple joins
END
ELSE
BEGIN
SELECT * INTO #TEMPTAB FROM different multiple joins
END
SELECT * FROM #TEMPTAB more large number of multiple joins & where & groupby
ERROR: There is already an object #TEMPTAB defined
-- Because of select * into in IF and ELSE both
I don't want to create a temp table prior cause it has a lot of columns to be defined.
Is there a way around it?

Answer 1

This was a fun problem for me that is... Well I figured out four ways to do it. One is with a view, one with a temp Table, one with a physical table, and one with a stored procedure and global temp table. Let me know if you have any questions.
View
DECLARE #Variable VARCHAR(10) = 'aa';
IF LEN(#Variable) > 1
BEGIN
EXEC('CREATE VIEW yourView AS SELECT ''Greater than 1'' col')
END
ELSE
BEGIN
EXEC('CREATE VIEW yourView AS SELECT ''Less than 1'' col')
END
SELECT *
FROM yourView;
DROP VIEW yourView;
Temp Table
DECLARE #Variable VARCHAR(100) = 'aa',
--Default value is 0
#percent INT = 0;
--If the length > 1, then change percent to 100 as to return the whole table
IF LEN(#Variable) > 1
SET #percent = 100;
--If the length <=1, then #percent stays 0 and you return 0 percent of the table
SELECT TOP(#percent) PERCENT 'Greater than 1' col INTO #TEMPTAB
--If you didn't populate the table with rows, then use this query to populate it
IF(#percent = 0)
BEGIN
INSERT INTO #TEMPTAB
SELECT 'Less than 1' col
END
/*your 1k lines of code here*/
SELECT *
FROM #TEMPTAB
--Cleanup
DROP TABLE #tempTab
Physical Table
DECLARE #Variable VARCHAR(10) = 'A';
IF len(#Variable) > 1
BEGIN
SELECT 'Greater than 1' col INTO TEMPTAB
END
ELSE
BEGIN
SELECT 'Less than 1' col INTO TEMPTAB2
END
IF OBJECT_ID('TEMPTAB2') IS NOT NULL
--SP_Rename doesn't work on temp tables so that's why it's an actual table
EXEC SP_RENAME 'TEMPTAB2','TEMPTAB','Object'
SELECT *
FROM TEMPTAB
DROP TABLE TEMPTAB;
Stored Procedure with Global Temp Table
IF OBJECT_ID('yourProcedure') IS NOT NULL
DROP PROCEDURE yourProcedure;
GO
CREATE PROCEDURE yourProcedure
AS
IF OBJECT_ID('tempdb..##TEMPTAB') IS NOT NULL
DROP TABLE ##tempTab;
SELECT 'Greater than 1' col INTO ##TEMPTAB
GO
DECLARE #Variable VARCHAR(10) = 'aaa';
IF LEN(#Variable) > 1
BEGIN
EXEC yourProcedure;
END
ELSE
BEGIN
SELECT 'Less than 1' col INTO ##TEMPTAB
END
SELECT *
FROM ##TEMPTAB
IF OBJECT_ID('tempdb..##TEMPTAB') IS NOT NULL
DROP TABLE ##TEMPTab;

Answer 2

Didn't you consider dynamic query with global temporary tables? This works for me:
DECLARE #sql NVARCHAR(MAX) = CASE WHEN 1 = 2
THEN 'SELECT * INTO ##TEMPTAB FROM dbo.SomeTable1'
ELSE 'SELECT * INTO ##TEMPTAB FROM dbo.SomeTable2'
END
EXEC (#sql)
SELECT * FROM ##TEMPTAB
DROP TABLE ##TEMPTAB

Answer 3

The first time you ran this code it created the table #TEMPTAB. The next time you ran SQL Server is telling you the table already exists. You should precede your code with the following:
if object_ID('tempdb..#TEMPTAB','U') is not null
drop table #TEMPTAB
This will drop (delete the table if it already exists) and the code that follows will always be able to recreate(or create) the table.