Saturday, March 29, 2008

Check If Temporary Table Exists

How do you check if a temp table exists?
You can use IF OBJECT_ID('tempdb..#temp') IS NOT NULL
Let's see how it works

--Create table
USE Norhtwind
GO

CREATE TABLE #temp(id INT)

--Check if it exists
IF OBJECT_ID('tempdb..#temp') IS NOT NULL
BEGIN
PRINT '#temp exists!'
END
ELSE
BEGIN
PRINT
'#temp does not exist!'
END

--Another way to check with an undocumented optional second parameter
IF OBJECT_ID('tempdb..#temp','u') IS NOT NULL
BEGIN
PRINT '#temp exists!'
END
ELSE
BEGIN
PRINT
'#temp does not exist!'
END



--Don't do this because this checks the local DB and will return does not exist
IF OBJECT_ID('tempdb..#temp','local') IS NOT NULL
BEGIN
PRINT '#temp exists!'
END
ELSE
BEGIN
PRINT
'#temp does not exist!'
END


--unless you do something like this
USE tempdb
GO

--Now it exists again
IF OBJECT_ID('tempdb..#temp','local') IS NOT NULL
BEGIN
PRINT '#temp exists!'
END
ELSE
BEGIN
PRINT
'#temp does not exist!'
END

--let's go back to Norhtwind again
USE Norhtwind
GO


--Check if it exists
IF OBJECT_ID('tempdb..#temp') IS NOT NULL
BEGIN
PRINT '#temp exists!'
END
ELSE
BEGIN
PRINT
'#temp does not exist!'
END

now open a new window from Query Analyzer (CTRL + N) and run this code again
--Check if it exists
IF OBJECT_ID('tempdb..#temp') IS NOT NULL
BEGIN
PRINT '#temp exists!'
END
ELSE
BEGIN
PRINT
'#temp does not exist!'
END


It doesn't exist and that is correct since it's a local temp table not a global temp table


Well let's test that statement
--create a global temp table
CREATE TABLE ##temp(id INT) --Notice the 2 pound signs, that's how you create a global variable

--Check if it exists
IF OBJECT_ID('tempdb..##temp') IS NOT NULL
BEGIN
PRINT '##temp exists!'
END
ELSE
BEGIN
PRINT
'##temp does not exist!'
END

It exists, right?
Now run the same code in a new Query Analyzer window (CTRL + N)

--Check if it exists
IF OBJECT_ID('tempdb..##temp') IS NOT NULL
BEGIN
PRINT '##temp exists!'
END
ELSE
BEGIN
PRINT
'##temp does not exist!'
END

And yes this time it does exist since it's a global table

7 comments:

D Dolcy said...

This post was a great help.
Thanks.
Dawn

Manisha Reddy said...

it's a great post. simple basics. But it was so useful. thanks

Joseph said...

This post is great.. Thank you

Madhu said...

Its really helpful, Thanks Man.
Thanks for your support.

AkAs said...

Simple and useful, Great Post!!

Arvin said...
This comment has been removed by the author.
Arvin said...

thanx. very helpful