MySQL check if value exist more than once

mysql

Solution

Ususlly you can do this using `GROUP BY` and `HAVING COUNT(*)>1`

SELECT USERNAME FROM CALLER
GROUP BY USERNAME 
HAVING COUNT(*)>1

Update: To get all duplicate rows:

SELECT * FROM CALLER WHERE USERNAME IN
  ( 
    SELECT USERNAME FROM CALLER
    GROUP BY USERNAME 
    HAVING COUNT(*)>1
  )

Problem

I have MySQL database and a have a table named CALLER. In table caller I need to check if in column USERNAME there are values which exist more than once and if exist to list all these values. Thank you

Original source