如何选择2个随机类别数据

Question

我的表结构如下（带有数据）：

+------------------------------------+
|id    fname     category  city      |
|1     ram       cook      kathmandu |
|2     shyam     cook      lalitpur  |
|3     krishna   maid      patan     |
|4     jay       maid      kupondole |
|5     rajan     maid      ratnapark |
+------------------------------------+

该查询应立即返回2行（厨师和女仆），并随机返回厨师和女仆。 我怎样才能做到这一点？

Answer 1

两种选择：

(SELECT * FROM TableName WHERE category='cook' ORDER BY rand() limit 1)
UNION ALL
(SELECT * FROM TableName WHERE category='maid' ORDER BY rand() limit 1)

在SQL Fiddle中查看结果。

要么

SELECT * FROM TableName 
WHERE category IN ('cook','maid') 
GROUP BY category 
ORDER BY rand() limit 2

在SQL Fiddle中查看结果。

结果：

ID  FNAME   CATEGORY    CITY
1   ram     cook        kathmandu
5   rajan   maid        ratnapark

Answer 2

select fname
from table
where category="cook"
order by RAND()
LIMIT 1
UNION
select fname
from table
where category="maid"
order by RAND()
LIMIT 1

Answer 3

子查询负责查找随机ID

SELECT *
FROM mytable
WHERE id IN
    (SELECT round(rand()*(max(id)-min(id)+1))+min(id)
     FROM mytable
     GROUP BY category);