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 * 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 inner join test on test.subject="shuxue" and user.name=test.name; +------+----------+-----------+----+----------+-------+---------+ | id | name | address | id | name | score | subject | +------+----------+-----------+----+----------+-------+---------+ | 1 | xiaoming | beijing | 1 | xiaoming | 89 | shuxue | | 3 | xiaohong | suzhou | 2 | xiaohong | 89 | shuxue | | 4 | xiaohei | changchun | 14 | xiaohei | 80 | shuxue | +------+----------+-----------+----+----------+-------+---------+ 3 rows in set (0.00 sec) mysql> select * from user,test where test.name=user.name and test.subject="shuxue"; +------+----------+-----------+----+----------+-------+---------+ | id | name | address | id | name | score | subject | +------+----------+-----------+----+----------+-------+---------+ | 1 | xiaoming | beijing | 1 | xiaoming | 89 | shuxue | | 3 | xiaohong | suzhou | 2 | xiaohong | 89 | shuxue | | 4 | xiaohei | changchun | 14 | xiaohei | 80 | shuxue | +------+----------+-----------+----+----------+-------+---------+ 3 rows in set (0.00 sec) mysql> select * from user,test where test.subject="shuxue" and test.name=user.name; +------+----------+-----------+----+----------+-------+---------+ | id | name | address | id | name | score | subject | +------+----------+-----------+----+----------+-------+---------+ | 1 | xiaoming | beijing | 1 | xiaoming | 89 | shuxue | | 3 | xiaohong | suzhou | 2 | xiaohong | 89 | shuxue | | 4 | xiaohei | changchun | 14 | xiaohei | 80 | shuxue | +------+----------+-----------+----+----------+-------+---------+ 3 rows in set (0.00 sec)