1、Case 子查询连接查询 代码如下:select * from score create database demo use demo create table [user] ( [uId] int identity( 1 ,1 ) primary key, [name] varchar ( 50), [level] int –1骨灰大虾菜鸟 ) insert into [user] ( name, level ) values (‘ 犀利哥 ‘, 1 ) insert into [user