mysql 表联结，内部联结

mysql> select * from user;
+------+----------+-----------+
| id   | name     | address   |
+------+----------+-----------+
|     | xiaoming | beijing   |
|     | xiaobai  | shandong  |
|     | xiaohong | suzhou    |
|     | xiaohei  | changchun |
+------+----------+-----------+
 rows in set (0.00 sec)

mysql> select * from test;
+----+------------+-------+-----------+
| id | name       | score | subject   |
+----+------------+-------+-----------+
|   | xiaoming   |     | shuxue    |
|   | xiaohong   |     | shuxue    |
|   | xiaohong   |     | english   |
|   | xiaohong   |     | physics   |
|   | xiaohong   |     | astronaut |
|   | xiaoming   |     | physics   |
|   | xiaoming   |     | astronaut |
|   | xiaoming   |     | english   |
|   | xiaobai    |     | astronaut |
|  | .2xiaobai |     | english   |
|  | .2xiaobai |     | physics   |
|  | 3xiaobai   |     | shuxue    |
|  | 123xiaohei |     | astronaut |
|  | xiaohei    |     | shuxue    |
|  | xiaohei    |     | physics   |
|  | .12xiaohei |     | english   |
+----+------------+-------+-----------+
 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 |
+------+----------+-----------+----+----------+-------+---------+
|     | xiaoming | beijing   |   | xiaoming |     | shuxue  |
|     | xiaohong | suzhou    |   | xiaohong |     | shuxue  |
|     | xiaohei  | changchun |  | xiaohei  |     | shuxue  |
+------+----------+-----------+----+----------+-------+---------+
 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 |
+------+----------+-----------+----+----------+-------+---------+
|     | xiaoming | beijing   |   | xiaoming |     | shuxue  |
|     | xiaohong | suzhou    |   | xiaohong |     | shuxue  |
|     | xiaohei  | changchun |  | xiaohei  |     | shuxue  |
+------+----------+-----------+----+----------+-------+---------+
 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 |
+------+----------+-----------+----+----------+-------+---------+
|     | xiaoming | beijing   |   | xiaoming |     | shuxue  |
|     | xiaohong | suzhou    |   | xiaohong |     | shuxue  |
|     | xiaohei  | changchun |  | xiaohei  |     | shuxue  |
+------+----------+-----------+----+----------+-------+---------+
 rows in set (0.00 sec)