SQL语句理解 select * from B where (select count(1) as num from A where A.ID = B.ID) = 0select * from B where (select count(1) as num from A where A.ID = B.ID) = 0请问如何理解,为什么 可以在B表中 排除A表的数据
来源:学生作业帮助网 编辑:作业帮 时间:2024/07/29 19:30:11
x)y~'XX85'5DAK!(?WI<#(UA*_WaXWQU`4z~.kzw*ġ:Ovz^t
W<ٱVYߤ38ygͣv6#+l
X|z:lɔ./{ַhߋ=@+Q
:xݼ}:jX$ف }M