Question

Me and another developer are discussing which type of table would be more appropriate for our task. It’s basically going to be a cache that we’re going to truncate at the end of the day. Personally, I don’t see any reason to use anything other than a normal table for this, but he wants to use a global temp table.

Are there any advantages to one or the other?

Answer 1

Use a normal table in tempdb if this is just transient data that you can afford to lose on service restart or a user database if the data is not that transient.

tempdb is slightly more efficient in terms of logging requirements.

Global temp tables get dropped once all referencing connections are the connection that created the table is closed.

Edit: Following @cyberkiwi’s edit. BOL does definitely explicitly say

Global temporary tables are visible to
any user and any connection after they
are created, and are deleted when all
users that are referencing the table
disconnect from the instance of SQL
Server.

In my test I wasn’t able to get this behaviour though either.

Connection 1

CREATE TABLE ##T (i int)
INSERT INTO ##T values (1)
SET CONTEXT_INFO 0x01

Connection 2

INSERT INTO ##T VALUES(4)
WAITFOR DELAY '00:01'
INSERT INTO ##T VALUES(5)

Connection 3

SELECT OBJECT_ID('tempdb..##T') 
declare @killspid varchar(10) = (select 'kill ' +  cast(spid as varchar(5)) from sysprocesses where context_info=0x01)
exec (@killspid)
SELECT OBJECT_ID('tempdb..##T') /*NULL - But 2 is still 
                                 running let alone disconnected!*/