mysql> INSERT IGNORE INTO person_tbl (last_name, first_name)

    -> VALUES( 'J', 'T');

Query OK, 1 row affected (0.00 sec)

mysql> INSERT IGNORE INTO person_tbl (last_name, first_name)

    -> VALUES( 'J', 'T');

Query OK, 0 rows affected (0.00 sec)

mysql> SELECT DISTINCT last_name, first_name

    -> FROM person_tbl;

mysql> SELECT last_name, first_name

    -> FROM person_tbl

    -> GROUP BY (last_name, first_name);

mysql> CREATE TABLE tmp SELECT last_name, first_name, sex FROM person_tbl  GROUP BY (last_name, first_name, sex);

mysql> DROP TABLE person_tbl;

mysql> ALTER TABLE tmp RENAME TO person_tbl;