mysql自关联
时间：2021-07-01 10:21:17
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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
mysql自关联
标签：nbsp HERE mysql sele 数据 course left join span mys
