How Can I Find and Retrieve Duplicate Records with Detailed Information in MySQL?

Finding Duplicate Records in MySQL with Detailed Information

It is often necessary to identify and remove duplicate records from a MySQL database for data integrity and efficiency purposes. While the common practice of using a GROUP BY query with a HAVING clause allows you to count duplicate records, it only provides a summarized view.

To retrieve the actual duplicate rows, a more comprehensive approach is required. Instead of relying on a separate query to look up the duplicates, you can utilize a subquery within the original statement.

The following query restructures the initial query as a subquery and joins it with the main table to extract the specific duplicate rows:

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;

This query yields the desired output:

JIM    JONES    100 MAIN ST
JOHN   SMITH    100 MAIN ST

This method effectively combines the aggregate operation with the retrieval of individual duplicate rows, providing detailed information without the need for additional queries.

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