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Finding Duplicate Records

Posted on 2002-07-24
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Last Modified: 2010-05-02
I'm using a Microsoft Access database (not created in Access) in VB6. I need to be able to detect duplicate records using SQL.

Each record has an InvoiceNumber field which is a Long. Each InvoiceNumber should be unique but I don't want to use an Index to make the InvoiceNumber unique. (I didn't design the database, I just have to work with it.)

I want to be able to create a recordset that contains all duplicate InvoiceNumbers in the database.
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Question by:bhlang
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RainUK earned 100 total points
ID: 7175070
Try this SQL Statement :

SELECT InvoiceNumber
FROM tablename
GROUP BY InvoiceNumber
HAVING
count(*) > 1


This will return a recordset of all invoice numbers which have been duplicated in the DB. By the way if you want to make the invoice number a unique, just set it as the Primary Key. This will throw an error if somebody then trys to insert another row with the same invoice number.

But remember to clear the duplicates first, otherwise primary key won't work.
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Expert Comment

by:jayeshshah
ID: 7175229
the sql would be

select InvoiceNumber, count(*) as Duplicatecount from tablename
group by Invoicenumber
where count(*) > 1


this shall return you all the duplicated Invoice Numbers as well as No of time each invoice number has been duplicated
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Author Comment

by:bhlang
ID: 7175247
Your code didn't work for me.
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Author Comment

by:bhlang
ID: 7175248
This code worked exactly as I wanted.
Thanks
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