我需要從類別+子類別+子類別中獲取文件的總數如何在mysql中取兩個不同查詢結果的總數?
爲此,我使用我的視圖編寫了這種類型的查詢。
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
它的返回計數值。但我想知道任何其他更好的方法可用於獲得相同的結果。
我試過這種方式,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)
。
,我會說總結3'COUNT'查詢會比服用'UNION'的'COUNT'更快。 – Amadan 2012-01-05 11:28:21
是的,我知道。但其三種觀點。我不想加入這些意見 – learner 2012-01-05 13:15:14