Question

我的列如下

name              |     cat
----------------------------------------
ala               |     games
alaa              |     software
aha               |     games
asd               |     games
aad               |     software
aas               |     software
asd               |     books
aad               |     software
aas               |     books

所以我有三个查询，如下面

SELECT * FROM `table` WHERE MATCH(`name`) AGAINST ('a*' IN BOOLEAN MODE) AND cat='games' LIMIT 2 
SELECT * FROM `table` WHERE MATCH(`name`) AGAINST ('a*' IN BOOLEAN MODE) AND cat='software' LIMIT 2
SELECT * FROM `table` WHERE MATCH(`name`) AGAINST ('a*' IN BOOLEAN MODE) AND cat='books' LIMIT 2

所以我想先获得2 result from each category（游戏，书籍，软件）......现在我使用这三个查询..如何将它们组合成一个查询..

P.s这只是一个例子..我正在处理多达10个类别..我想要一些不浪费太多资源的东西

Answer 1

假设这些查询有效，请使用UNION：

SELECT DISTINCT * FROM `table` WHERE MATCH(`name`) 
   AGAINST ('a*' IN BOOLEAN MODE) LIMIT 2 WHERE cat='games'
UNION
SELECT DISTINCT * FROM `table` WHERE MATCH(`name`) 
   AGAINST ('a*' IN BOOLEAN MODE) LIMIT 2 WHERE cat='books'
UNION 
SELECT DISTINCT * FROM `table` WHERE MATCH(`name`) 
   AGAINST ('a*' IN BOOLEAN MODE) LIMIT 2 WHERE cat='software'

关于优化，documentation状态＆＃34;当将LIMIT row_count与DISTINCT组合时，MySQL会在找到row_count唯一行时立即停止。＆＃34;所以你应该添加它来限制各个查询的资源。

将单个查询中的多个WHERE与LIMIT 2组合在一起

1 个答案: