mysql多表连接查询(去掉重复列)

三个数据库

1

2

3

多表连接查询,且去掉重复列,使用 USING()

select * from (select * from school left join course USING (courseid)) e left join student USING (studentid);

select * from school left join course USING (courseid)相当于

select * from school left join course on school.courseid=course.courseid;