现有三张表
teacher表:
id name
1 大炮
2 机枪
3 老师
grade表:
id gradename
1 小班
2 大班
3 中班
grade_teacher表:
id gradeid teacherid
1 1 1
2 2 1
3 3 1
最后这张是关系表,意思就是一个老师可能给很多的班级上课,现在就是想把这个一个老师给那些班级上课查询出来
呼叫各位大神! 这个该怎么写
select teacher.name,grade.gradename from teacher inner join grade inner join grade_teacher as gd where teacher.id = gd.teacherid and grade.id = gd.gradeid groupBy gd.teacherid
分组查询
http://blog.csdn.net/spring_great/article/details/47272261
就两个表关联。。。根据老师id到关联表查出他关联的班级id直接联表的出班级的信息
select teacher.name, grade.gradename
from grade_teacher gd
inner join grade
on grade.id = gd.gradeid
inner join teacher
on teacher.id = gd.teacherid
group By teacher.name, gd.teacherid
select t.name,g.gradename from grade_teacher gt left join teacher t on gt.teacherid=t.id left join grade g on gt. gradeid =g.id