mysql - SQL查询将一列的组结果带入多个列

Question

尝试进行生成这种结果的查询

EmpId,  EmpSickLeave,EmpCasualLeave, EmpAnnualLeave, TotalLeave
1,       1,           0,                0            1
2,       0,           0,                2            2
3,       0,           1,                0            1
4,       0,           1,                0            1  
5,       1,           0,                0            1

我有两张 table

表 EmpLeave::包含一列 EmpId、Date、EmpLeaveTypeID

表 EmpLeaveType::包括 EmpLeaveTypeID 和 LeaveName

表格中的数据

EmpLeaveType Table
EmpLeaveTypeID , LeaveName
1,              Sick Leave
2,              Annual
3,              Casual

EmpLeave Table
column EmpId, Date, EmpLeaveTypeID
            1, 2015-07-01, 1
            3, 2015-07-02, 2
            5, 2015-07-04, 1
            4, 2015-07-04, 2
            2, 2015-07-05, 2
            2, 2015-07-07, 2

我正在拉扯我的头发，无法带来这种结果。这可能吗？

  EEmpId,  EmpSickLeave,EmpCasualLeave, EmpAnnualLeave, TotalLeave
1,       1,           0,                0            1
2,       0,           0,                2            2
3,       0,           1,                0            1
4,       0,           1,                0            1  
5,       1,           0,                0            1

我试过这个错误的东西!

    SELECT * count(EmpLeaveTypeID) FROM `EmpLeaveType`
WHERE SwitchDate Between '2015-07-01' AND '2015-07-28'
group by EmpLeaveType, EmpId

Answer 1

请尝试下面的 SELECT 查询。它没有考虑有一天可能会更改休假类型。 SQL fiddle 链接 http://sqlfiddle.com/#!9/0fd13/2 该查询只是执行条件聚合来计算每个员工的休假时间。

SELECT 
EmpId, 
SUM(CASE WHEN EmpLeaveTypeID=1 THEN 1 ELSE 0 END) as EmpSickLeave,
SUM(CASE WHEN EmpLeaveTypeID=2 THEN 1 ELSE 0 END) as EmpCasualLeave,
SUM(CASE WHEN EmpLeaveTypeID=3 THEN 1 ELSE 0 END) as EmpAnnualLeave,
COUNT(1) as TotalLeave
FROM `EmpLeave`
WHERE Date Between '2015-07-01' AND '2015-07-28'
group by EmpId