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MySQL: Finding Oldest Douplicate

Posted on 2014-02-11
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Last Modified: 2014-02-11
The returns the bookkey and updated time of duplicate items:
SELECT elqBooks.isbn, elqBooks.updated
 FROM elqBooks 
 GROUP BY elqBooks.ISBN HAVING count(elqBooks.isbn) > 1

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I want the OLDEST item to be selected.  How can I get the OLDEST matching duplicated item?
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Question by:hankknight
3 Comments
 
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Dan Craciun earned 500 total points
ID: 39850012
SELECT elqBooks.isbn, MIN(elqBooks.updated)
 FROM elqBooks
 GROUP BY elqBooks.ISBN HAVING count(elqBooks.isbn) > 1
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by:hankknight
ID: 39850068
Thanks.  Now how can I do this with the bookkey only?  I only want the bookkey of the oldest douplicate record to be included.
SELECT elqBooks.bookkey
 FROM elqBooks 
 GROUP BY elqBooks.ISBN HAVING count(elqBooks.isbn) > 1

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LVL 11

Expert Comment

by:John_Vidmar
ID: 39850188
Without knowing your schema, would you be able to take the results of the group-by/min and join back to your table to get the key?
SELECT	a.bookkey
FROM	elqBooks	a
JOIN	(	SELECT	isbn
		,	updated = MIN(updated)
		FROM	elqBooks 
		GROUP
		BY	isbn
		HAVING	count(*) > 1 
	)	b	ON	a.isbn = b.isbn
			AND	a.updated = b.updated

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