mysql - 如何在同一查询中从具有不同条件的表中选择数据

Question

我有一个表，我想从这个表中选择数据，条件为 type =1 , type =2, type =3 并且每个类型限制为 5。

如果我使用下面的命令，3 个表相互连接 );所以我有 5x5x5 = 125 条记录!

SELECT * 
FROM 
( 
  ( select * from `question` where type = 1 limit 5) as t1 , 
  (select * from `question` where type = 2 limit 5) as t2, 
  (select * from `question` where type = 3 limit 5) as t3
)

如何只用 1 个命令选择此数据，使我的表有 15 条记录？

Answer 1

(SELECT * FROM question WHERE type = 1 LIMIT 5)
UNION
(SELECT * FROM question WHERE type = 2 LIMIT 5)
UNION
(SELECT * FROM question WHERE type = 3 LIMIT 5)