数据库中表的连接代码与实现

首先分别创建两个表

INSERT INTO tba(a1,a2) VALUE(1,2),(3,4)
INSERT INTO tbb(b1,b2) VALUE(5,6),(7,8)

笛卡尔积

SELECT * FROM tba,tbb

内连接

SELECT *FROM tba INNER JOIN tbb ON tba.a1=tbb.b1;

左外链接

SELECT *FROM tba LEFT JOIN tbb ON tba.a1=tbb.b1;

右外连接

SELECT*FROM tba RIGHT JOIN tbb ON tba.a1=tbb.b1;

全外链接

SELECT*FROM tba LEFT JOIN tbb ON tba.a1=tbb.b1
UNION	
SELECT*FROM tba RIGHT JOIN tbb ON tba.a1=tbb.b1;