Get list of duplicate rows in MySql

Question

i have a table like this

ID     nachname     vorname
1       john         doe
2       john         doe
3       jim          doe
4       Michael     Knight
         


        

Answer 1

The general solution to your problem is a query of the form

SELECT col1, col2, count(*)
FROM t1
GROUP BY col1, col2
HAVING count(*) > 1

This will return one row for each set of duplicate row in the table. The last column in this result is the number of duplicates for the particular values.

---

If you really want the ID, try something like this:

SELECT id FROM 
t1, 
( SELECT col1, col2, count(*)
  FROM t1
  GROUP BY col1, col2
  HAVING count(*) > 1 ) as t2
WHERE t1.col1 = t2.col1 AND t1.col2 = t2.col2 

Haven't tested it though