問題描述

![我需要統(tǒng)計各個layerid對應(yīng)的U、A是多少。比如 HYD_NET_LN U 5 A 10 HYD_VAL_PT U 8 A 25 應(yīng)該如何寫][1]

問題解答

簡單點，不知道這樣可不可以。SELECT layerid,ChangeMold,COUNT(ChangeMold) FROM table_name GROUP BY layerid,ChangeMold

select count(*),layid,changeMold from tbl group by layid,changeMold

SELECT layerid,sum(case when changeMold=’U’ then 1 else 0 end) changeMold_U,sum(case when changeMold=’A’ then 1 else 0 end) changeMold_AFROM table_name GROUP BY layerid;回答4：

如果 要 統(tǒng)計這種大文件 的話 。還是都查出來 然后再處理數(shù)組方便點（sql比較弱 ）

select layerid,changeMold,count(*) as num from TABLE where layerid in (select layerid from TABLE group by layerid) group by changeMold; 這條sql的性能很不好