Mysql CASE WHEN 用法

select
sum(1) as col_0_0_, sum(case vciinfo.useable when -1 then 1 else 0 end) as col_1_0_,
sum(case when vciinfo.activatetime is null then 0 else 1 end) as col_2_0_
from vci_info vciinfo

這是一個用case when 實現統計表中不同狀態數據數量的sql語句

這里要注意的是 判斷字段是否為空用 case when vciinfo.activatetime is null   

判斷值 case vciinfo.useable when -1

 

when 的位置不同