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Starting Member

8 Posts

Posted - 03/04/2013 :  10:11:04  Show Profile  Reply with Quote
Hi all,

I want to remove some duplicates from a table.

The structure of the table is as follows:

ID, Contact, School

And the duplicates are listed as follows:

1 Bob 200
2 Bob 200
3 Jim 10
4 John 30
5 Wang 40
6 Wang 40

Any help would be highly appreciated

Best Regards

Flowing Fount of Yak Knowledge

6062 Posts

Posted - 03/04/2013 :  10:30:44  Show Profile  Reply with Quote
Assuming that (Contact, School) constitute your logical key then this should work. You can run the SELECT first and if you like the results then run the DELETE.

select t.*
--delete t
from   (
       select contact, school, min(id) idToKeep
       from   <table>
       group by contact, school
       having count(*) > 1
       ) dupes
inner join <table> t
       on t.contact = dupes.contact
       and t.school = dupes.school
where  t.id > dupes.idToKeep

Once that is done then you should put a UNIQUE constraint on the table to prevent more duplicate values.

Be One with the Optimizer
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Starting Member

8 Posts

Posted - 03/05/2013 :  06:55:19  Show Profile  Reply with Quote
Thank you that works like a charm.

Best Regards
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