One example is here
create table t1(col1 int, col2 int, col3 char(50))
insert into t1 values (1, 1, 'data value one')
insert into t1 values (1, 1, 'data value one')
insert into t1 values (1, 2, 'data value

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

delete from t1
where col1=1 and col2=1