Question

我的桌子名为“出勤”，如下所示：

Sno  SecurityGroup  SecurityName  Designation   AttendanceStatus
----------------------------------------------------------------
1    JJ             Ram           officer       present
2    JJ             Raja          Guards        Present
3    JJ             Rani          LadyGuards    Present
4    JJ             Ramu          officer       present

我需要输出作为每个指定中存在的证券数量的计数如下：

SecutityGroup Officer  Guards  LadyGuards
-----------------------------------------
JJ              2        1         1

有人可以帮我写一个查询来获得这个输出吗？

Answer 1

select SecurityGroup,
    sum(case when Designation = 'officer' then 1 end) as Officer,
    sum(case when Designation = 'Guards' then 1 end) as Guards,
    sum(case when Designation = 'LadyGuards' then 1 end) as LadyGuards 
from Attendance
group by SecurityGroup

或者，如果您可以在行中获取信息，则可以执行以下操作：

select SecurityGroup, Designation, count(*) as Count
from Attendance
group by SecurityGroup, Designation

显然第二种方法是优选的，因为它不那么脆弱，并且如果在没有任何修改的情况下添加更多Designations，它将起作用。

Answer 2

这也可以使用PIVOT完成，具体取决于您的数据库：

SELECT SecurityGroup, SUM([officer]) AS Officers, SUM([Guards]) AS Guards, SUM([LadyGuards]) AS LadyGuards
FROM Attendance
PIVOT
    (
        COUNT(Sno)
        FOR Designation IN ([officer], [Guards], [LadyGuards])
    ) as pvt
WHERE AttendanceStatus = 'Present'
GROUP BY SecurityGroup

如果您希望根据表中的内容动态生成列列表，则会变得更难，但这样可以避免需要大量子查询。

Answer 3

 select distinct SecurityGroup,
    select sum(*) from Attendance where designation = 'officer') as Officer,
    select sum(*) from Attendance where designation = 'Guards') as Guards,
    select sum(*) from Attendance where designation = 'LadyGuards') as LadyGuards    
from Attendance

Answer 4

您可以使用子查询来完成此任务：

SELECT
  SecurityGroup,
  (SELECT COUNT(*) FROM `Attendance` WHERE `Designation` = "officer") AS `Officer`,
  (SELECT COUNT(*) FROM `Attendance` WHERE `Designation` = "Guards") AS `Guards`,
  (SELECT COUNT(*) FROM `Attendance` WHERE `Designation` = "LadyGuards") AS `LadyGuards`
FROM `Attendance`
WHERE `SecurityGroup` = "JJ"

我实际上没有测试过这个查询，因为我只想和你分享这个概念。

另外请注意，这不是完成所需工作的最快方法，但我相信这是最简单的方法。

我希望这适合你。

Answer 5

我在SQL中尝试使用PIVOT但是我无法获得计数值.. 以下是我试过的代码：

select SecurityGroup,Officer,Guards,LadyGuards from 
(select SecurityGroup,rDesignation from Attendance 
where SecurityGroup='jj') up
PIVOT (count(Designation) for Designation IN 
(Officer,Guards,LadyGuards)) as pvt

当我执行此查询时，我明白了 SecurityGroup，官，逆天，LadyGuards JJ，0,0,0

而不是， SecurityGroup，官，逆天，LadyGuards JJ，2,1,1

在这种情况下如何编写SQL查询

5 个答案: