mysql自关联和多表连接查询

自关联操作

多表连接查询 inner join 内查询 left join 左查询 right join 右查询

select student.id,student.name,classes.name from student inner join classes on student.cls_id = classes.id;

inner join内连 left join左连 right join右连表名join 表名 on 连接字段

select student.name,course_student.cid from student left join course_student on student.id = course_student.sid;

以student.id与course_student.sid连接匹配,打印student.name,course_student.cid

select student.name,course.name from student left join course_student on student.id = course_student.sid left join course on course_student.cid =course.id; 三表(2明细表+1关系表)相连取交集打印学生名字与课程名字

select * from areas as p inner join areas as a on p.aid = a.pid where p.atitle = '河南省';

省、市，两表查询在一张表里(as起别名)用上级id打印，

select * from areas as p inner join areas as c on c.pid = p.aid inner join areas as a on a.pid = c.aid where a.atitle = '二七区';

省、市、区，三表查询在一张表里(as起别名)用上级id打印区表title为‘二七区’的数据

select * from from areas as p inner join areas as c on c.pid = p.aid inner join areas as as a on a.pid = c.aid where p.atitle = '河南省';

打印河南省所有的市和所有的区

巴特西

mysql自关联和多表连接查询

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