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| Submitted on: |
11/10/2000 4:00:14 PM |
| By: |
Greg
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| Level: |
Beginner |
| User Rating: |
By 10 Users |
| Compatibility: |
SQL Server 7.0 |
| Views: |
21738 |
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Allows you to determine duplicate rows in a table and provide a count of the duplicates.
It's helped me find a row or two that had left me with "inconclusive" results in the past : )
Ciao;
Greg
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--**************************************
-- Name: FindDupes
-- Description:Allows you to determine duplicate rows in a table and provide a count of the duplicates.
It's helped me find a row or two that had left me with "inconclusive" results in the past : )
Ciao;
Greg
-- By: Greg
--
-- Assumes:Limiting the columns provides field level duplicate finds..
Using all columns will give a row level duplicate find.
--
--This code is copyrighted and has-- limited warranties.Please see http://www.Planet-Source-Code.com/vb/scripts/ShowCode.asp?txtCodeId=247&lngWId=5--for details.--**************************************
SELECT column1, column2, column3, ... n, COUNT(*) AS [Number of Dupes]
FROM TableName
GROUP BY column1, column2, column3... n
HAVING COUNT(*) > 1
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Other User Comments
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 1/30/2001 4:40:38 PM: todde
does anyone know how to find the row in the above statement with the GREATEST NUMBER of dups without using a second query or a view?
todde@metalwest.com
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1/31/2001 9:36:17 AM: Greg
Try the derived table method...
SELECT Column1
FROM (SELECT COLUMN1, COUNT(*) AS 'Amount'
FROM TableName
GROUP BY Column1
HAVING COUNT(*) = (SELECT MAX (B.Amount)
FROM (SELECT COUNT(*) AS 'Amount'
FROM TableName
GROUP BY Column1
HAVING COUNT(*) > 1) AS B)
) AS A
GROUP BY Column1
Hope the formatting is okay.
Ciao;
Greg
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2/18/2001 3:20:42 AM: Brian Bender
Great Job!
Take this one step further. How would you write a query that deletes the dupes and leaves only one behind?
Email me please: brianbender77@hotmail.com
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2/28/2001 9:23:58 AM: Greg
Sorry it took so long...
Deleting data is always risky.
I would suggest multi-staging an approach such as
1) Find dupes
2) query to get PK's based on dupes
3) delete based on PK's -1
Bottom line... thee are many ways this could be accomplished and they depend on the structure of your table(s).
Ciao;
Greg
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12/10/2002 8:38:46 AM:
Thanks, helped a lot!
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