周六，早十点起床，毕竟劳动了一周了，偶尔偷个小懒！ 步入正题！ ----注---/*这只是我随便写的表名，大概意思往下看*/--------select case when b.val is null then a.valwhen b.val <= 0 then a.val else a.val / a.qty end as RTL_VAL from 表1 a left joi