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)