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

You can do it with a self-join:

select distinct t1.id from t as t1 inner join t as t2 
on t1.col1=t2.col1 and t1.col2=t2.col2 and t1.id<>t2.id

the t1.id<>t2.id is necessary to avoid ids matching against themselves. (If you want only 1 row out of each set of duplicates, you can use t1.id).