mysql插入数据时，去掉重复的数据；

mysql> INSERT IGNORE INTOperson_tbl (last_name, first_name)
    -> VALUES( 'J', 'T');
Query OK, 1 row affected (0.00sec)
mysql> INSERT IGNORE INTOperson_tbl (last_name, first_name)
    -> VALUES( 'J', 'T');
Query OK, 0 rows affected (0.00 sec)

mysql> SELECT DISTINCTlast_name, first_name
    -> FROM person_tbl;

mysql> SELECTlast_name, first_name
    -> FROMperson_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 TABLEperson_tbl;
mysql> ALTER TABLE tmp RENAME TO person_tbl;