从具有不同where子句的表中选择

Question

我有一张桌子

EmpAttendance

Date    EmpId Attendance
1/1/12   Emp1   P
1/1/12   Emp2   P
2/1/12   Emp1   P
2/1/12   Emp2   A

由此，我想要一份报告，显示所有员工的总体呈现和缺席

AttendanceReport
EmpId    Presents    Absents
Emp1      2            0
Emp2      1            1

请帮帮我

Answer 1

按empid分组并使用案例仅总结礼物和缺席

select empid, 
       sum(case when attendance = 'P' then 1 end) as presents,
       sum(case when attendance = 'A' then 1 end) as absents
from EmpAttendance
group by empid