mysql - sql查詢統計
問題描述
![我需要統計各個layerid對應的U、A是多少。比如 HYD_NET_LN U 5 A 10 HYD_VAL_PT U 8 A 25 應該如何寫][1]
問題解答
回答1: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
回答3: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 統計這種大文件 的話 。還是都查出來 然后再處理數組方便點(sql比較弱 )
回答5: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
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