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how to update one record when there are duplicates?

Posted on 1998-08-20
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Last Modified: 2010-03-19
Is there a way to update only one record when there are duplicate records in the table?  
The reason there are duplicates is because the distinct key fields haven't been populated yet, but I need to perform an update on only one particular record before I can fill in the distinct key fields.  Any suggestions?
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Question by:Lorik
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7 Comments
 
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Expert Comment

by:mcix
ID: 1089671
An easy way would be to have an identity field in your table.  On the insert, you could return the @@Identity variable to your code from a stored proc that does the insert.  With that value, you would have a unique criteria for the where clause for the update.

If you can't modify the table struct, there are possibly other ways.
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by:bret
ID: 1089672
I know this would work in Sybase SQL Server, not sure in MS SQL, but give it a try (on a test table, please!).
-- limit action to a single row
set rowcount 1
go
update mytable
where dupkeyvalue = <x>
go
-- return to affecting full set of rows
set rowcount 0
go

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Author Comment

by:Lorik
ID: 1089673
MS-SQL doesn't have ROWCOUNT funtion, I wish it did.
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by:mcix
ID: 1089674
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DennisH earned 100 total points
ID: 1089675
SQL Server does not allow selected updates unless there is a primary key designated for a table.
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by:mayhew
ID: 1089676
Lorik,

I'm not sure I understand exactly what you're trying to do.  If I understand your question, you might want to do an UPDATE...WHERE, something like:

UPDATE table SET <whatever>
WHERE <afield> = (select distinct <afield> from table)

This may give you a starting point, again depending on what exactly you want to do.

Don
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Expert Comment

by:mayhew
ID: 1089677
Lorik,

Sorry, I wasn't thinking straight.  What I wrote before will not work.  Please ignore it.

If you want to update only one row, you have to find something unique about it.  It doesn't have to be a key, but it has to be unique.  

Otherwise you have to do something procedural like using a cursor to find the set, fetch the first record and then update it.  Let us know if you need help with this.  :)

Don
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