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SQL Server 2005 DELETE Query

Posted on 2014-10-10
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Last Modified: 2014-11-24
I have a sql server 2005 database that has one table in particular with approx. 800,000 rows. I need to delete all but one row of this table for troubleshooting purposes.

Looking at the table there appears to be a column called 'SEQ' which contains numbers that appear to be unique to each row. I wish to pick one of these numbers randomly and delete all rows except that one.

What would be the best way to achieve this goal?
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Question by:dowhatyoudo22
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Guy Hengel [angelIII / a3] earned 1000 total points
ID: 40373065
it depends on what you call "best"

if this is a test table, just rename it, recreate it with the old name, and copy just 1 record back. this should assign it a new SEQ number , unless you want to keep the "exact" value, in which case: http://technet.microsoft.com/en-us/library/aa259221%28v=sql.80%29.aspx

to get 1 random record:
select top 1 * from yourtable order by newid()
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Expert Comment

by:John_Vidmar
ID: 40373073
Assuming there is no referential-integrity that would prevent you from deleting a record:
-- grab the record(s) into a temporary table
SELECT * INTO #temp FROM YourTable WHERE something = whatever

-- delete all rows, avoiding transaction-log
TRUNCATE TABLE YourTable

-- insert the record(s) captured earlier
INSERT YourTable SELECT * FROM #temp

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Assisted Solution

by:Vitor Montalvão
Vitor Montalvão earned 1000 total points
ID: 40373081
You can save a record randomly (use Guy's suggestion) and the TRUNCATE the table (deletes all records without logging) and then put back the saved record:
SELECT TOP 1 * 
INTO #tempTable
FROM yourTable 
ORDER BY newid()

TRUNCATE yourTable

INSERT INTO yourTable
SELECT * FROM #tempTable

DROP #tempTable 

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Expert Comment

by:Mohammed Khawaja
ID: 40373413
I agree with Vitor, his solution is elegant and easy to deploy.  If it makes you feel better, you could run the query "select top 1  * from yourtable", copy the information to notepad or save the results to a file and then truncate the table.
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Expert Comment

by:Scott Pletcher
ID: 40373581
For the record, truncating a table does *not* "avoid logging", it reduces it.
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