Question

一张员工表里面3W条数据，写一条最有效率的SQL语句查出

age>30,salary>9000、age>30,salary<9000、age<30,salary>9000、age<30,salary<9000的人数。

Answer 1

select
sum(case when age>30 and salary>9000 then 1 else 0 end) [team1],
sum(case when age>30 and salary<9000 then 1 else 0 end) [team2],
sum(case when age<30 and salary>9000 then 1 else 0 end) [team3],
sum(case when age<30 and salary<9000 then 1 else 0 end) [team4]
from 表名

Answer 2

select count(*) from 员工 where age>30 and salary>9000 or age>30 and salary<9000 or age<30 and salary>9000 or age<30 and salary<9000