mysql中join用法解析
实例数据库如下：
student表：
mysql> select * from student; +-----------+-----------+------+------+-------+ | sno | sname | ssex | sage | sdept | +-----------+-----------+------+------+-------+ | 201215121 | 李勇 | 男 | 22 | cs | | 201215122 | 刘晨 | 女 | 19 | cs | | 201215123 | 王敏 | 女 | 18 | ma | | 201215125 | 张立 | 男 | 19 | is | | 201215128 | 陈冬 | 男 | 18 | is | | 201215126 | 张成民 | 男 | 18 | cs | +-----------+-----------+------+------+-------+6 rows in set (0.00 sec)
sc表：
mysql> select * from sc; +-----------+------+-------+ | sno | cno | grade | +-----------+------+-------+ | 201215121 | 1 | 92 | | 201215121 | 2 | 85 | | 201215121 | 3 | 88 | | 201215122 | 2 | 90 | | 201215122 | 3 | 80 | | 201215128 | 1 | 78 | +-----------+------+-------+6 rows in set (0.00 sec)
left join（左连接）
sql语句如下：
select * from student left join sc on student.sno=sc.sno;
运行结果如下：
+-----------+-----------+------+------+-------+-----------+------+-------+ | sno | sname | ssex | sage | sdept | sno | cno | grade | +-----------+-----------+------+------+-------+-----------+------+-------+ | 201215121 | 李勇 | 男 | 22 | cs | 201215121 | 1 | 92 | | 201215121 | 李勇 | 男 | 22 | cs | 201215121 | 2 | 85 | | 201215121 | 李勇 | 男 | 22 | cs | 201215121 | 3 | 88 | | 201215122 | 刘晨 | 女 | 19 | cs | 201215122 | 2 | 90 | | 201215122 | 刘晨 | 女 | 19 | cs | 201215122 | 3 | 80 | | 201215128 | 陈冬 | 男 | 18 | is | 201215128 | 1 | 78 | | 201215123 | 王敏 | 女 | 18 | ma | null | null | null | | 201215125 | 张立 | 男 | 19 | is | null | null | null | | 201215126 | 张成民 | 男 | 18 | cs | null | null | null | +-----------+-----------+------+------+-------+-----------+------+-------+
在此例中left join 是以student表中的记录为基础，student表可以看成左表，sc表可以看成右表，左表中的记录会完全显示出来，加上匹配到的右表，如果左边没有匹配到，则其余部分显示为null。
using字句using字句和on字句，类似，但结果略有不同。
例如：
mysql> select student.sno,sname,grade from student left join sc on student.sno=sc.sno; +-----------+-----------+-------+ | sno | sname | grade | +-----------+-----------+-------+ | 201215121 | 李勇 | 92 | | 201215121 | 李勇 | 85 | | 201215121 | 李勇 | 88 | | 201215122 | 刘晨 | 90 | | 201215122 | 刘晨 | 80 | | 201215128 | 陈冬 | 78 | | 201215123 | 王敏 | null | | 201215125 | 张立 | null | | 201215126 | 张成民 | null | +-----------+-----------+-------+ 9 rows in set (0.00 sec)
以上等价于
select sno,sname,grade from student left join sc using(sno); +-----------+-----------+-------+ | sno | sname | grade | +-----------+-----------+-------+ | 201215121 | 李勇 | 92 | | 201215121 | 李勇 | 85 | | 201215121 | 李勇 | 88 | | 201215122 | 刘晨 | 90 | | 201215122 | 刘晨 | 80 | | 201215128 | 陈冬 | 78 | | 201215123 | 王敏 | null | | 201215125 | 张立 | null | | 201215126 | 张成民 | null | +-----------+-----------+-------+
不同的地方，例如：
select * from student left join sc on student.sno=sc.sno; +-----------+-----------+------+------+-------+-----------+------+-------+ | sno | sname | ssex | sage | sdept | sno | cno | grade | +-----------+-----------+------+------+-------+-----------+------+-------+ | 201215121 | 李勇 | 男 | 22 | cs | 201215121 | 1 | 92 | | 201215121 | 李勇 | 男 | 22 | cs | 201215121 | 2 | 85 | | 201215121 | 李勇 | 男 | 22 | cs | 201215121 | 3 | 88 | | 201215122 | 刘晨 | 女 | 19 | cs | 201215122 | 2 | 90 | | 201215122 | 刘晨 | 女 | 19 | cs | 201215122 | 3 | 80 | | 201215128 | 陈冬 | 男 | 18 | is | 201215128 | 1 | 78 | | 201215123 | 王敏 | 女 | 18 | ma | null | null | null | | 201215125 | 张立 | 男 | 19 | is | null | null | null | | 201215126 | 张成民 | 男 | 18 | cs | null | null | null | +-----------+-----------+------+------+-------+-----------+------+-------+
select * from student left join sc using (sno); +-----------+-----------+------+------+-------+------+-------+ | sno | sname | ssex | sage | sdept | cno | grade | +-----------+-----------+------+------+-------+------+-------+ | 201215121 | 李勇 | 男 | 22 | cs | 1 | 92 | | 201215121 | 李勇 | 男 | 22 | cs | 2 | 85 | | 201215121 | 李勇 | 男 | 22 | cs | 3 | 88 | | 201215122 | 刘晨 | 女 | 19 | cs | 2 | 90 | | 201215122 | 刘晨 | 女 | 19 | cs | 3 | 80 | | 201215128 | 陈冬 | 男 | 18 | is | 1 | 78 | | 201215123 | 王敏 | 女 | 18 | ma | null | null | | 201215125 | 张立 | 男 | 19 | is | null | null | | 201215126 | 张成民 | 男 | 18 | cs | null | null | +-----------+-----------+------+------+-------+------+-------+
重复的sno列，如果用on字句会被输出两次
right join（右连接）同left join，只不过以右表为基础，例如：
select * from student right join sc using (sno); +-----------+------+-------+--------+------+------+-------+ | sno | cno | grade | sname | ssex | sage | sdept | +-----------+------+-------+--------+------+------+-------+ | 201215121 | 1 | 92 | 李勇 | 男 | 22 | cs | | 201215121 | 2 | 85 | 李勇 | 男 | 22 | cs | | 201215121 | 3 | 88 | 李勇 | 男 | 22 | cs | | 201215122 | 2 | 90 | 刘晨 | 女 | 19 | cs | | 201215122 | 3 | 80 | 刘晨 | 女 | 19 | cs | | 201215128 | 1 | 78 | 陈冬 | 男 | 18 | is | +-----------+------+-------+--------+------+------+-------+
inner join（相等连接或内连接）
不会显示以谁为基础，只会显示符合条件的记录
select * from student inner join sc on student.sno=sc.sno; +-----------+--------+------+------+-------+-----------+------+-------+ | sno | sname | ssex | sage | sdept | sno | cno | grade | +-----------+--------+------+------+-------+-----------+------+-------+ | 201215121 | 李勇 | 男 | 22 | cs | 201215121 | 1 | 92 | | 201215121 | 李勇 | 男 | 22 | cs | 201215121 | 2 | 85 | | 201215121 | 李勇 | 男 | 22 | cs | 201215121 | 3 | 88 | | 201215122 | 刘晨 | 女 | 19 | cs | 201215122 | 2 | 90 | | 201215122 | 刘晨 | 女 | 19 | cs | 201215122 | 3 | 80 | | 201215128 | 陈冬 | 男 | 18 | is | 201215128 | 1 | 78 | +-----------+--------+------+------+-------+-----------+------+-------+
以上语句等同于：
select * from student,sc where student.sno=sc.sno; +-----------+--------+------+------+-------+-----------+------+-------+ | sno | sname | ssex | sage | sdept | sno | cno | grade | +-----------+--------+------+------+-------+-----------+------+-------+ | 201215121 | 李勇 | 男 | 22 | cs | 201215121 | 1 | 92 | | 201215121 | 李勇 | 男 | 22 | cs | 201215121 | 2 | 85 | | 201215121 | 李勇 | 男 | 22 | cs | 201215121 | 3 | 88 | | 201215122 | 刘晨 | 女 | 19 | cs | 201215122 | 2 | 90 | | 201215122 | 刘晨 | 女 | 19 | cs | 201215122 | 3 | 80 | | 201215128 | 陈冬 | 男 | 18 | is | 201215128 | 1 | 78 | +-----------+--------+------+------+-------+-----------+------+-------+
扩展如果只想从a表中取出一些记录，但不包含b表
可以在left join 后面加上一个where语句
select * from student left join sc using(sno) where sc.sno is null; +-----------+-----------+------+------+-------+------+-------+ | sno | sname | ssex | sage | sdept | cno | grade | +-----------+-----------+------+------+-------+------+-------+ | 201215123 | 王敏 | 女 | 18 | ma | null | null | | 201215125 | 张立 | 男 | 19 | is | null | null | | 201215126 | 张成民 | 男 | 18 | cs | null | null | +-----------+-----------+------+------+-------+------+-------+
求差集
可以结合union字句，由于本例中，右侧的已经全部对应的所以显示结果，和上一个一致。
select * from student left join sc using(sno) where student.sno is null union select * from student left join sc using(sno) where sc.sno is null; +-----------+-----------+------+------+-------+------+-------+ | sno | sname | ssex | sage | sdept | cno | grade | +-----------+-----------+------+------+-------+------+-------+ | 201215123 | 王敏 | 女 | 18 | ma | null | null | | 201215125 | 张立 | 男 | 19 | is | null | null | | 201215126 | 张成民 | 男 | 18 | cs | null | null | +-----------+-----------+------+------+-------+------+-------+
full join
select * from student left join sc on student.sno=sc.sno union select * from student right join sc on student.sno=sc.sno; +-----------+-----------+------+------+-------+-----------+------+-------+ | sno | sname | ssex | sage | sdept | sno | cno | grade | +-----------+-----------+------+------+-------+-----------+------+-------+ | 201215121 | 李勇 | 男 | 22 | cs | 201215121 | 1 | 92 | | 201215121 | 李勇 | 男 | 22 | cs | 201215121 | 2 | 85 | | 201215121 | 李勇 | 男 | 22 | cs | 201215121 | 3 | 88 | | 201215122 | 刘晨 | 女 | 19 | cs | 201215122 | 2 | 90 | | 201215122 | 刘晨 | 女 | 19 | cs | 201215122 | 3 | 80 | | 201215128 | 陈冬 | 男 | 18 | is | 201215128 | 1 | 78 | | 201215123 | 王敏 | 女 | 18 | ma | null | null | null | | 201215125 | 张立 | 男 | 19 | is | null | null | null | | 201215126 | 张成民 | 男 | 18 | cs | null | null | null | +-----------+-----------+------+------+-------+-----------+------+-------+
注：a left join b 等同于 b right join a
mysql> select * from student left join sc using(sno); +-----------+-----------+------+------+-------+------+-------+ | sno | sname | ssex | sage | sdept | cno | grade | +-----------+-----------+------+------+-------+------+-------+ | 201215121 | 李勇 | 男 | 22 | cs | 1 | 92 | | 201215121 | 李勇 | 男 | 22 | cs | 2 | 85 | | 201215121 | 李勇 | 男 | 22 | cs | 3 | 88 | | 201215122 | 刘晨 | 女 | 19 | cs | 2 | 90 | | 201215122 | 刘晨 | 女 | 19 | cs | 3 | 80 | | 201215128 | 陈冬 | 男 | 18 | is | 1 | 78 | | 201215123 | 王敏 | 女 | 18 | ma | null | null | | 201215125 | 张立 | 男 | 19 | is | null | null | | 201215126 | 张成民 | 男 | 18 | cs | null | null | +-----------+-----------+------+------+-------+------+-------+ 9 rows in set (0.00 sec)mysql> select * from sc right join student using(sno); +-----------+-----------+------+------+-------+------+-------+ | sno | sname | ssex | sage | sdept | cno | grade | +-----------+-----------+------+------+-------+------+-------+ | 201215121 | 李勇 | 男 | 22 | cs | 1 | 92 | | 201215121 | 李勇 | 男 | 22 | cs | 2 | 85 | | 201215121 | 李勇 | 男 | 22 | cs | 3 | 88 | | 201215122 | 刘晨 | 女 | 19 | cs | 2 | 90 | | 201215122 | 刘晨 | 女 | 19 | cs | 3 | 80 | | 201215128 | 陈冬 | 男 | 18 | is | 1 | 78 | | 201215123 | 王敏 | 女 | 18 | ma | null | null | | 201215125 | 张立 | 男 | 19 | is | null | null | | 201215126 | 张成民 | 男 | 18 | cs | null | null | +-----------+-----------+------+------+-------+------+-------+
mysql中join用法解析实例数据库如下：
student表：
mysql> select * from student; +-----------+-----------+------+------+-------+ | sno | sname | ssex | sage | sdept | +-----------+-----------+------+------+-------+ | 201215121 | 李勇 | 男 | 22 | cs | | 201215122 | 刘晨 | 女 | 19 | cs | | 201215123 | 王敏 | 女 | 18 | ma | | 201215125 | 张立 | 男 | 19 | is | | 201215128 | 陈冬 | 男 | 18 | is | | 201215126 | 张成民 | 男 | 18 | cs | +-----------+-----------+------+------+-------+ 6 rows in set (0.00 sec)
sc表：
mysql> select * from sc; +-----------+------+-------+ | sno | cno | grade | +-----------+------+-------+ | 201215121 | 1 | 92 | | 201215121 | 2 | 85 | | 201215121 | 3 | 88 | | 201215122 | 2 | 90 | | 201215122 | 3 | 80 | | 201215128 | 1 | 78 | +-----------+------+-------+ 6 rows in set (0.00 sec)
left join（左连接）
sql语句如下：
select * from student left join sc on student.sno=sc.sno;
运行结果如下：
+-----------+-----------+------+------+-------+-----------+------+-------+ | sno | sname | ssex | sage | sdept | sno | cno | grade | +-----------+-----------+------+------+-------+-----------+------+-------+ | 201215121 | 李勇 | 男 | 22 | cs | 201215121 | 1 | 92 | | 201215121 | 李勇 | 男 | 22 | cs | 201215121 | 2 | 85 | | 201215121 | 李勇 | 男 | 22 | cs | 201215121 | 3 | 88 | | 201215122 | 刘晨 | 女 | 19 | cs | 201215122 | 2 | 90 | | 201215122 | 刘晨 | 女 | 19 | cs | 201215122 | 3 | 80 | | 201215128 | 陈冬 | 男 | 18 | is | 201215128 | 1 | 78 | | 201215123 | 王敏 | 女 | 18 | ma | null | null | null | | 201215125 | 张立 | 男 | 19 | is | null | null | null | | 201215126 | 张成民 | 男 | 18 | cs | null | null | null | +-----------+-----------+------+------+-------+-----------+------+-------+
在此例中left join 是以student表中的记录为基础，student表可以看成左表，sc表可以看成右表，左表中的记录会完全显示出来，加上匹配到的右表，如果左边没有匹配到，则其余部分显示为null。
using字句using字句和on字句，类似，但结果略有不同。
例如：
mysql> select student.sno,sname,grade from student left join sc on student.sno=sc.sno; +-----------+-----------+-------+| sno | sname | grade | +-----------+-----------+-------+| 201215121 | 李勇 | 92 | | 201215121 | 李勇 | 85 | | 201215121 | 李勇 | 88 | | 201215122 | 刘晨 | 90 | | 201215122 | 刘晨 | 80 | | 201215128 | 陈冬 | 78 | | 201215123 | 王敏 | null | | 201215125 | 张立 | null || 201215126 | 张成民 | null | +-----------+-----------+-------+9 rows in set (0.00 sec)
以上等价于
select sno,sname,grade from student left join sc using(sno); +-----------+-----------+-------+| sno | sname | grade | +-----------+-----------+-------+| 201215121 | 李勇 | 92 | | 201215121 | 李勇 | 85 | | 201215121 | 李勇 | 88 | | 201215122 | 刘晨 | 90 | | 201215122 | 刘晨 | 80 | | 201215128 | 陈冬 | 78 | | 201215123 | 王敏 | null | | 201215125 | 张立 | null || 201215126 | 张成民 | null | +-----------+-----------+-------+
不同的地方，例如：
select * from student left join sc on student.sno=sc.sno; +-----------+-----------+------+------+-------+-----------+------+-------+ | sno | sname | ssex | sage | sdept | sno | cno | grade | +-----------+-----------+------+------+-------+-----------+------+-------+ | 201215121 | 李勇 | 男 | 22 | cs | 201215121 | 1 | 92 | | 201215121 | 李勇 | 男 | 22 | cs | 201215121 | 2 | 85 | | 201215121 | 李勇 | 男 | 22 | cs | 201215121 | 3 | 88 | | 201215122 | 刘晨 | 女 | 19 | cs | 201215122 | 2 | 90 | | 201215122 | 刘晨 | 女 | 19 | cs | 201215122 | 3 | 80 | | 201215128 | 陈冬 | 男 | 18 | is | 201215128 | 1 | 78 | | 201215123 | 王敏 | 女 | 18 | ma | null | null | null | | 201215125 | 张立 | 男 | 19 | is | null | null | null | | 201215126 | 张成民 | 男 | 18 | cs | null | null | null | +-----------+-----------+------+------+-------+-----------+------+-------+
select * from student left join sc using (sno); +-----------+-----------+------+------+-------+------+-------+ | sno | sname | ssex | sage | sdept | cno | grade | +-----------+-----------+------+------+-------+------+-------+ | 201215121 | 李勇 | 男 | 22 | cs | 1 | 92 | | 201215121 | 李勇 | 男 | 22 | cs | 2 | 85 | | 201215121 | 李勇 | 男 | 22 | cs | 3 | 88 | | 201215122 | 刘晨 | 女 | 19 | cs | 2 | 90 | | 201215122 | 刘晨 | 女 | 19 | cs | 3 | 80 | | 201215128 | 陈冬 | 男 | 18 | is | 1 | 78 | | 201215123 | 王敏 | 女 | 18 | ma | null | null | | 201215125 | 张立 | 男 | 19 | is | null | null | | 201215126 | 张成民 | 男 | 18 | cs | null | null | +-----------+-----------+------+------+-------+------+-------+
重复的sno列，如果用on字句会被输出两次
right join（右连接）同left join，只不过以右表为基础，例如：
select * from student right join sc using (sno); +-----------+------+-------+--------+------+------+-------+ | sno | cno | grade | sname | ssex | sage | sdept | +-----------+------+-------+--------+------+------+-------+ | 201215121 | 1 | 92 | 李勇 | 男 | 22 | cs | | 201215121 | 2 | 85 | 李勇 | 男 | 22 | cs | | 201215121 | 3 | 88 | 李勇 | 男 | 22 | cs | | 201215122 | 2 | 90 | 刘晨 | 女 | 19 | cs | | 201215122 | 3 | 80 | 刘晨 | 女 | 19 | cs | | 201215128 | 1 | 78 | 陈冬 | 男 | 18 | is | +-----------+------+-------+--------+------+------+-------+
inner join（相等连接或内连接）
不会显示以谁为基础，只会显示符合条件的记录
select * from student inner join sc on student.sno=sc.sno; +-----------+--------+------+------+-------+-----------+------+-------+ | sno | sname | ssex | sage | sdept | sno | cno | grade | +-----------+--------+------+------+-------+-----------+------+-------+ | 201215121 | 李勇 | 男 | 22 | cs | 201215121 | 1 | 92 | | 201215121 | 李勇 | 男 | 22 | cs | 201215121 | 2 | 85 | | 201215121 | 李勇 | 男 | 22 | cs | 201215121 | 3 | 88 | | 201215122 | 刘晨 | 女 | 19 | cs | 201215122 | 2 | 90 | | 201215122 | 刘晨 | 女 | 19 | cs | 201215122 | 3 | 80 | | 201215128 | 陈冬 | 男 | 18 | is | 201215128 | 1 | 78 | +-----------+--------+------+------+-------+-----------+------+-------+
以上语句等同于：
select * from student,sc where student.sno=sc.sno; +-----------+--------+------+------+-------+-----------+------+-------+ | sno | sname | ssex | sage | sdept | sno | cno | grade | +-----------+--------+------+------+-------+-----------+------+-------+ | 201215121 | 李勇 | 男 | 22 | cs | 201215121 | 1 | 92 | | 201215121 | 李勇 | 男 | 22 | cs | 201215121 | 2 | 85 | | 201215121 | 李勇 | 男 | 22 | cs | 201215121 | 3 | 88 | | 201215122 | 刘晨 | 女 | 19 | cs | 201215122 | 2 | 90 | | 201215122 | 刘晨 | 女 | 19 | cs | 201215122 | 3 | 80 | | 201215128 | 陈冬 | 男 | 18 | is | 201215128 | 1 | 78 | +-----------+--------+------+------+-------+-----------+------+-------+
扩展如果只想从a表中取出一些记录，但不包含b表
可以在left join 后面加上一个where语句
select * from student left join sc using(sno) where sc.sno is null; +-----------+-----------+------+------+-------+------+-------+ | sno | sname | ssex | sage | sdept | cno | grade | +-----------+-----------+------+------+-------+------+-------+ | 201215123 | 王敏 | 女 | 18 | ma | null | null | | 201215125 | 张立 | 男 | 19 | is | null | null | | 201215126 | 张成民 | 男 | 18 | cs | null | null | +-----------+-----------+------+------+-------+------+-------+
求差集
可以结合union字句，由于本例中，右侧的已经全部对应的所以显示结果，和上一个一致。
select * from student left join sc using(sno) where student.sno is null union select * from student left join sc using(sno) where sc.sno is null; +-----------+-----------+------+------+-------+------+-------+ | sno | sname | ssex | sage | sdept | cno | grade | +-----------+-----------+------+------+-------+------+-------+ | 201215123 | 王敏 | 女 | 18 | ma | null | null | | 201215125 | 张立 | 男 | 19 | is | null | null | | 201215126 | 张成民 | 男 | 18 | cs | null | null | +-----------+-----------+------+------+-------+------+-------+
full join
select * from student left join sc on student.sno=sc.sno union select * from student right join sc on student.sno=sc.sno; +-----------+-----------+------+------+-------+-----------+------+-------+ | sno | sname | ssex | sage | sdept | sno | cno | grade | +-----------+-----------+------+------+-------+-----------+------+-------+ | 201215121 | 李勇 | 男 | 22 | cs | 201215121 | 1 | 92 | | 201215121 | 李勇 | 男 | 22 | cs | 201215121 | 2 | 85 | | 201215121 | 李勇 | 男 | 22 | cs | 201215121 | 3 | 88 | | 201215122 | 刘晨 | 女 | 19 | cs | 201215122 | 2 | 90 | | 201215122 | 刘晨 | 女 | 19 | cs | 201215122 | 3 | 80 | | 201215128 | 陈冬 | 男 | 18 | is | 201215128 | 1 | 78 | | 201215123 | 王敏 | 女 | 18 | ma | null | null | null | | 201215125 | 张立 | 男 | 19 | is | null | null | null | | 201215126 | 张成民 | 男 | 18 | cs | null | null | null | +-----------+-----------+------+------+-------+-----------+------+-------+
注：a left join b 等同于 b right join a
mysql> select * from student left join sc using(sno); +-----------+-----------+------+------+-------+------+-------+ | sno | sname | ssex | sage | sdept | cno | grade | +-----------+-----------+------+------+-------+------+-------+ | 201215121 | 李勇 | 男 | 22 | cs | 1 | 92 | | 201215121 | 李勇 | 男 | 22 | cs | 2 | 85 | | 201215121 | 李勇 | 男 | 22 | cs | 3 | 88 | | 201215122 | 刘晨 | 女 | 19 | cs | 2 | 90 | | 201215122 | 刘晨 | 女 | 19 | cs | 3 | 80 | | 201215128 | 陈冬 | 男 | 18 | is | 1 | 78 | | 201215123 | 王敏 | 女 | 18 | ma | null | null | | 201215125 | 张立 | 男 | 19 | is | null | null | | 201215126 | 张成民 | 男 | 18 | cs | null | null | +-----------+-----------+------+------+-------+------+-------+ 9 rows in set (0.00 sec)mysql> select * from sc right join student using(sno); +-----------+-----------+------+------+-------+------+-------+ | sno | sname | ssex | sage | sdept | cno | grade | +-----------+-----------+------+------+-------+------+-------+ | 201215121 | 李勇 | 男 | 22 | cs | 1 | 92 | | 201215121 | 李勇 | 男 | 22 | cs | 2 | 85 | | 201215121 | 李勇 | 男 | 22 | cs | 3 | 88 | | 201215122 | 刘晨 | 女 | 19 | cs | 2 | 90 | | 201215122 | 刘晨 | 女 | 19 | cs | 3 | 80 | | 201215128 | 陈冬 | 男 | 18 | is | 1 | 78 | | 201215123 | 王敏 | 女 | 18 | ma | null | null | | 201215125 | 张立 | 男 | 19 | is | null | null | | 201215126 | 张成民 | 男 | 18 | cs | null | null | +-----------+-----------+------+------+-------+------+-------+
以上就是mysql中join用法解析的内容。