一、查詢SQL格式：
SELECT <>
FROM <>
[LEFT、RIGHT] JOIN <>
WHERE <>
GROUP BY <>
HAVINT <>
ORDER BY<>
LIMIT <>,<>

二、“A 且 排除B”方式查詢：

A 且 非B

1、使用連接查詢
SELECT <> FROM a LEFT JOIN b ON a.id = b.id WHERE b.id IS NULL
巧妙利用連接查詢特點(diǎn)，將a表的在b表中無對應(yīng)項(xiàng)的記錄查出
2、使用EXISTS關(guān)鍵字查詢
SELECT <> FROM a WHERE NOT EXISTS ( SELECT * FROM b WHERE a.id = b.id )

三、MySQL中代替“FULL JOIN”的用法：
MySQL中無“FULL JOIN”的用法，可使用UNION關(guān)鍵字拼接左右連接查詢語句并對查詢結(jié)果去重，最終實(shí)現(xiàn)需要的查詢

A 且 B

SELECT <> FROM a LEFT JOIN b ON a.id = b.id
UNION
SELECT <> FROM a RIGHT JOIN b ON a.id = b.id

A且B且非AB

SELECT <> FROM a LEFT JOIN b ON a.id = b.id WHERE b.id IS NULL
UNION
SELECT <> FROM a RIGHT JOIN b ON a.id = b.id WHERE a.id IS NULL