我需要从类别+子类别+子类别中获取文件的总数如何在mysql中取两个不同查询结果的总数?
为此,我使用我的视图编写了这种类型的查询。
select ((select count(*) from view_category where 1=1)+ (select count(*) from view sub category where 1=1) + (select count(*) from view subsub category where 1=1)) as cnt
它的返回计数值。但我想知道任何其他更好的方法可用于获得相同的结果。
我试过这种方式,但它不工作(How to SUM() multiple subquery rows in MySQL?)
select sum(int_val) from((select count(*) from view_category where 1=1) as int_val union (select count(*) from view sub category where 1=1) as int_val union (select count(*) from view subsub category where 1=1) as int_val)
。
,我会说总结3'COUNT'查询会比服用'UNION'的'COUNT'更快。 – Amadan 2012-01-05 11:28:21
是的,我知道。但其三种观点。我不想加入这些意见 – learner 2012-01-05 13:15:14