1.内连接.两个表的公共部分用Inner join,Inner join是交集的部分. Select * from TableA A inner join TableB B on A.key=B.key 2.左外连接.A表和B表的共有,加上A的独有,简称全A. Select * from TableA A left join TableB B on A.key=B.key 红色部分是两表的公有部分,此时8号记录是A表的独有,右边的部门表并没有满足的就用null补齐. 3.右外连接.A表和B表的共
--表stuid name 1, Jack2, Tom3, Kity4, nono--表examid grade1, 562, 7611, 89 内连接 (显示两表id匹配的)select stu.id,exam.id,stu.name, exam.grade from stu inner join exam on stu.id=exam.idstu.id exam.id name grade--------------------------------1 1 Jack 562 2 Tom 7