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