Local Temporary Tables and Table Variables

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Local Temporary Tables and Table Variables

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Gail Shaw SSC Guru Points: 1004504 More actions · Answer 1

Yes, I did.

Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
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SQLRNNR SSC Guru Points: 281334 More actions · Answer 2

Thanks. That is what I thought.

Jason...AKA CirqueDeSQLeil
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smeet.sinha Mr or Mrs. 500 Points: 577 More actions · Answer 3

One more major diff.

You can not use temp tables in UDF

But can use table variables in UDF....

Jeff Moden SSC Guru Points: 1004406 More actions · Answer 4

True enough. You should also mention that most UDFs aren't necessary either. 🙂

--Jeff Moden

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First step towards the paradigm shift of writing Set Based code:
________Stop thinking about what you want to do to a ROW... think, instead, of what you want to do to a COLUMN.

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Graham_Day Ten Centuries Points: 1103 More actions · Answer 5

GilaMonster (8/31/2008)
Very nice.
Just one small thing. You say that for data storage, temp tables are in TempDB and table variables are in memory and tempDB. I may be misunderstanding what you mean there, but temp tables are also memory resident unless it becomes necessary to write them to disk (memory pressure, too large a table)

Also, the Appendix states that table variables are held in memory and temporary tables are held in tempdb. Whilst usually correct*, it is also the case that both are physically created in tempdb, as can be demonstrated by running the following code on a SQL Server which has no other activity occurring (runs on SQL 2000, 2005 and 2008):

-- make a list of all of the user tables currently active in the

-- TempDB database

if object_id('tempdb..#tempTables') isnot null droptable #tempTables

select name into #tempTables from tempdb..sysobjectswhere type ='U'

-- prove that even this new temporary table is in the list.

-- Note the suffix at the end of it to uniquely identify the table across sessions.

select * from #tempTables where name like '#tempTables%'

GO

-- create a table variable

declare@MyTableVariable table (RowID int)

-- show all of the new user tables in the TempDB database.

select name from tempdb..sysobjects

where type ='U' and name notin (select name from #tempTables)

GO

* According to KB305977, a table variable can hold more data than could fit into memory.

http://support.microsoft.com/default.aspx?scid=kb;en-us;305977&Product=sql2k