Question

我有以下4个选择：

 select english,type from table where type='brief' ORDER BY RAND() LIMIT 5;
 select english,type from table where type='small' ORDER BY RAND() LIMIT 5;
 select english,type from table where type='medium' ORDER BY RAND() LIMIT 5;
 select english,type from table where type='large';

而不是进行多次查询，我宁愿将其作为一个UNION运行 - 也看到所有输出的格式相同。

我尝试了以下但是RAND（）似乎不起作用。每种类型大约有10个选项，但我一直看到相同的5而不是随机返回：

 select english,type from table where type='brief' LIMIT 5
 UNION
 select english,type from table where type='small' LIMIT 5
 UNION
 select english,type from table where type='medium' LIMIT 5
 UNION
 select english,type from table where type='large' ORDER BY type,RAND();

有关如何以真正的随机回报运行此UNION的任何建议吗？

THX

Answer 1

如果您想通过整个联盟订购，您需要将联合包含在另一个选项中，如下所示：

SELECT (
select english,type from table where type='brief' LIMIT 5
UNION
select english,type from table where type='small' LIMIT 5
UNION
select english,type from table where type='medium' LIMIT 5
UNION
select english,type from table where type='large'
)
ORDER BY type, RAND();

Mysql +帮助创建一个UNION查询

1 个答案: