SELECT mycol,

COUNT(mycol)

FROM mytable

GROUP BY mycol

HAVING COUNT(mycol) > 1;

SELECT mycol1, COUNT(mycol1),

mycol2, COUNT(mycol2),

mycol3, COUNT(mycol3)

FROM mytable

GROUP BY mycol1,

mycol2,

mycol3

HAVING COUNT(mycol1) > 1

AND COUNT(mycol2) > 1

AND COUNT(mycol3) > 1;