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How do I loop through each row in a table variable

Posted on 2009-04-14
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Last Modified: 2012-05-06
For MS SQL 2005. I have a table variable with no ID column. How do I loop through each row, or how do I create an ID column so I can loop through it?
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Question by:NobleRLC
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8 Comments
 
LVL 18

Expert Comment

by:UnifiedIS
ID: 24141659
What do you hope to accomplish by looping through the table?
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BrandonGalderisi earned 500 total points
ID: 24141684
I'm with unified in that you probably don't need to loop.  But here is how you define an ID column in your table variable.

declare @SomeTable table
  (ident       int identity primary key clustered
  ,field1       ......
....
)
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LVL 22

Expert Comment

by:dportas
ID: 24141685
The simple answer is: Don't. It's better to avoid looping through rows one at a time by writing set-based queries instead. Also, every table should have a key. There's no excuse for not having one on a table variable.
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Author Comment

by:NobleRLC
ID: 24141832
I'm passing variables from the table variable to a stored procedure executed on each row.
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Expert Comment

by:dportas
ID: 24142012
You could pass all the rows to the proc as a table-valued parameter.
Or you could write the proc so that it works on the whole result instead of one row at a time.

Try to avoid writing procs that need to be called for every single row. Doing it that way greatly increases the complexity of your code and destroys performance and scalability.
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Expert Comment

by:BrandonGalderisi
ID: 24142134
Table valued parameters aren't available until 2008. :)  But the rest is all valid about doing procs to work with data sets not rows.
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Expert Comment

by:Chris Luttrell
ID: 24142149
When you have to do something like that we avoid cursors and do something like the code below, assuming that you have to leave the original table alone and that your values are unique so the delete just deletes the one:

Select Variable 
into #TmpTable  -- could be table variable, but you have to set it up
from Table
 
DECLARE @thisVariable [typeneeded]
WHILE EXISTS (SELECT * FROM #tmpTable)
BEGIN
	SELECT TOP 1 @thisVariable = Variable FROM #TmpTable
	
	EXEC yourStoredProcedure (@thisVariable)
	
	DELETE FROM #TmpTable WHERE Variable = @thisVariable
END
DROP TABLE #TmpTable

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Expert Comment

by:dportas
ID: 24142275
If you must call a proc for each row then I suggest you use an explicit DECLARE CURSOR iwith the FAST_FORWARD option. Using a cursor has the advantage over SELECT TOP because you can specify the order without having to requery the whole table on each iteration of the loop. Also a DECLARE CURSOR arguably makes it more explicit what is happening in loop.
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