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Temporary tables and Table variables – MsSQL

Temporary Tables

The simple answer is yes you can. Let look at a simple CREATE TABLE statement:

CREATE TABLE #Yaks (
YakID int,
YakName char(30) )

Temporary tables are created in tempdb. If you run this query:

CREATE TABLE #Yaks (
YakID int,
YakName char(30) )

select name
from tempdb..sysobjects 
where name like '#yak%'

drop table #yaks

Another Example

CREATE TABLE #TibetanYaks(
YakID int,
YakName char(30) )

INSERT INTO #TibetanYaks (YakID, YakName)
SELECT 	YakID, YakName
FROM 	dbo.Yaks
WHERE 	YakType = 'Tibetan'

-- Do some stuff with the table

drop table #TibetanYaks

Table Variables

If you are using SQL Server 2000 or higher, you can take advantage of the new TABLE variable type. These are similar to temporary tables except with more flexibility and they always stay in memory.  The code above using a table variable might look like this:

DECLARE @TibetanYaks TABLE (
YakID int,
YakName char(30) )

INSERT INTO @TibetanYaks (YakID, YakName)
SELECT 	YakID, YakName
FROM 	dbo.Yaks
WHERE 	YakType = 'Tibetan'

-- Do some stuff with the table

Example

DECLARE @TibetanYaks TABLE (
YakID int,
YakName char(30) )

INSERT INTO @TibetanYaks (YakID, YakName)
SELECT 	YakID, YakName
FROM 	dbo.Yaks
WHERE 	YakType = 'Tibetan'

UPDATE 	@TibetanYaks
SET 	YakName = UPPER(YakName)

SELECT *
FROM @TibetanYaks

Global Temporary Tables

You can also create global temporary tables. These are named with two pound signs. For example, ##YakHerders is a global temporary table. Global temporary tables are visible to all SQL Server connections. When you create one of these, all the users can see it.  These are rarely used in SQL Server.

Summary

That shows you an example of creating a temporary table, modifying it, and returning the values to the calling program. I hope this gives you what you were looking for.

Based on: http://www.sqlteam.com/article/temporary-tables

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