MySql学习之Join查询

一、SQL执行顺序

1、手写sql顺序

2、机读sql顺序

二、7种Join的sql编写

注：图中 full outer join在mysql中是不支持的。可通过

1、全有

SELECT <select_list> FROM TableA A LEFT JOIN TableB B ON A.Key = B.Key
UNION
SELECT <select_list> FROM TableA A RIGHT JOIN TableB B ON A.Key = B.Key

2、A的独有和B的独有

SELECT <select_list> FROM TableA A LEFT JOIN TableB B ON A.Key = B.Key WHERE B.Key IS NULL
UNION
SELECT <select_list> FROM TableA A RIGHT JOIN TableB B ON A.Key = B.Key WHERE A.Key IS NULL