mysql - sql查询统计

问题描述

![我需要统计各个layerid对应的U、A是多少。比如 HYD_NET_LN U 5 A 10 HYD_VAL_PT U 8 A 25 应该如何写][1]

问题解答

简单点，不知道这样可不可以。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 统计这种大文件 的话 。还是都查出来 然后再处理数组方便点（sql比较弱 ）

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