mysqlduplicates

Find duplicate records in MySQL


I want to pull out duplicate records in a MySQL Database. This can be done with:

SELECT address, count(id) as cnt FROM list
GROUP BY address HAVING cnt > 1

Which results in:

100 MAIN ST    2

I would like to pull it so that it shows each row that is a duplicate. Something like:

JIM    JONES    100 MAIN ST
JOHN   SMITH    100 MAIN ST

Any thoughts on how this can be done? I'm trying to avoid doing the first one then looking up the duplicates with a second query in the code.


Solution

  • The key is to rewrite this query so that it can be used as a subquery.

    SELECT firstname, 
       lastname, 
       list.address 
    FROM list
       INNER JOIN (SELECT address
                   FROM   list
                   GROUP  BY address
                   HAVING COUNT(id) > 1) dup
               ON list.address = dup.address;