mysql> select * from test -> ;+----+------------+-------+-----------+| id | name | score | subject |+----+------------+-------+-----------+| 1 | xiaoming | 89 | shuxue || 2 | xiaohong | 89 | shuxue || 3 | xiaohong | 80 | english || 4 | xiaohong | 80 | physics || 5 | xiaohong | 80 | astronaut || 6 | xiaoming | 80 | physics || 7 | xiaoming | 80 | astronaut || 8 | xiaoming | 80 | english || 9 | xiaobai | 80 | astronaut || 10 | 1.2xiaobai | 80 | english || 11 | 2.2xiaobai | 80 | physics || 12 | 3xiaobai | 80 | shuxue || 13 | 123xiaohei | 80 | astronaut || 14 | xiaohei | 80 | shuxue || 15 | xiaohei | 80 | physics || 16 | .12xiaohei | 80 | english |+----+------------+-------+-----------+16 rows in set (0.00 sec)mysql> select * from user;+------+----------+-----------+| id | name | address |+------+----------+-----------+| 1 | xiaoming | beijing || 2 | xiaobai | shandong || 3 | xiaohong | suzhou || 4 | xiaohei | changchun |+------+----------+-----------+4 rows in set (0.00 sec)mysql> select id,name from user where name="xiaohong" union select id,name from test where name="xiaoming";+------+----------+| id | name |+------+----------+| 3 | xiaohong || 1 | xiaoming || 6 | xiaoming || 7 | xiaoming || 8 | xiaoming |+------+----------+5 rows in set (0.00 sec)mysql> select id,name from user where name="xiaohong" union all select id,name from test where name="xiaoming";+------+----------+| id | name |+------+----------+| 3 | xiaohong || 1 | xiaoming || 6 | xiaoming || 7 | xiaoming || 8 | xiaoming |+------+----------+5 rows in set (0.00 sec)mysql> select id,name from user where name="xiaohong" union all select id,name from test where name="xiaoming" order by id;+------+----------+| id | name |+------+----------+| 1 | xiaoming || 3 | xiaohong || 6 | xiaoming || 7 | xiaoming || 8 | xiaoming |+------+----------+5 rows in set (0.00 sec)