在 SELECT CASE 中选择其他数据答案

【问题标题】：Select Other Data in SELECT CASE在 SELECT CASE 中选择其他数据
【发布时间】：2017-11-12 20:18:26
【问题描述】：

查询返回 StudentId 和 HaveGift，现在我想在 (studentId) 返回时使用另一个选择从 tbl_Students (StuName,StuLName,...) 中查找学生信息。返回 HaveGift No 的 SQL：

CREATE PROCEDURE SelectGiftsTest
    @StudentId              INT,
    @DateMinCur     NVARCHAR(12),
    @DateMaxCur     NVARCHAR(12),
    @DateMinPrev    NVARCHAR(12),
    @DateMaxPrev    NVARCHAR(12)

AS
    WITH Prev AS
(
    SELECT StudentId, ISNULL(SUM(Score),0) As HighScoreUser
FROM (SELECT StudentId, Score FROM tbl_ActPoint
UNION ALL
      SELECT StudentId, Score FROM tbl_EvaPoint     WHERE Date>=@DateMinPrev AND Date <= @DateMaxPrev   AND StudentId = @StudentId
      ) as T 
      GROUP BY  StudentId
),
Cur AS 
(
    SELECT StudentId, ISNULL(SUM(Score),0) As HighScoreUser
FROM (SELECT StudentId, Score FROM tbl_ActPoint
UNION ALL
      SELECT StudentId, Score FROM tbl_EvaPoint     WHERE Date>=@DateMinCur AND Date <= @DateMaxCur     AND StudentId = @StudentId
      ) as T 
      GROUP BY  StudentId
) 
SELECT CASE 
        WHEN(Prev.HighScoreUser <= Cur.HighScoreUser)
        THEN 'Yes'
        ELSE 'No'
        END as HaveGift,Prev.StudentId

FROM Prev
INNER JOIN Cur
ON Prev.StudentId = Cur.StudentId
WHERE Prev.StudentId=@StudentId
RETURN 0

【问题讨论】：

您期望 HaveGift = YES？到底是什么问题？
我想根据返回的 studentId 从 tbl_student 中选择学生信息。

标签： sql sql-server select stored-procedures select-case

【解决方案1】：

查看您的代码时，您在 prev 和 cur 中求和 tbl_ActPoint 的分数表，但您想比较 tbl_EvaPoint 差异。

我解释一下：

你比较A+B（第一个联合）和A+C（第二个联合），你只能比较B和C。

我已经像这样修改了您的查询：

with Total as (
    SELECT StudentId, 
    sum(case when Date between @DateMinPrev AND @DateMaxPrev then score else end) ScorePrev, 
    sum(case when Date between @DateMinCur AND @DateMaxCur then score else end) ScoreCur, 
    FROM tbl_ActPoint 
    where StudentId = @StudentId and (Date between @DateMinPrev AND @DateMaxPrev or Date between @DateMinCur AND @DateMaxCur)
    group by StudentId
)
select 
CASE WHEN(ScorePrev <= ScoreCur) THEN 'Yes' ELSE 'No' END as HaveGift, tbl_student.* 
from tbl_student std left outer join total on std.StudentId = Total.StudentId

如果你也想要当前的分数，你可以这样做：

with Total as (
    SELECT StudentId, 
    sum(case when Date between @DateMinPrev AND @DateMaxPrev then score else end) ScorePrev, 
    sum(case when Date between @DateMinCur AND @DateMaxCur then score else end) ScoreCur, 
    FROM tbl_ActPoint 
    where StudentId = @StudentId and (Date between @DateMinPrev AND @DateMaxPrev or Date between @DateMinCur AND @DateMaxCur)
    group by StudentId
),
CurrentScoreUser as (
    SELECT StudentId, sum(Score) CurrentScore FROM tbl_ActPoint group by StudentId
)

select 
CASE WHEN(ScorePrev <= ScoreCur) THEN 'Yes' ELSE 'No' END as HaveGift, CurrentScoreUser.CurrentScore, 
tbl_student.* 
from tbl_student std left outer join Total on std.StudentId = Total.StudentId
left outer join CurrentScoreUser on CurrentScoreUser.StudentId=tbl_student.StudentId

【讨论】：

【解决方案2】：

如果我正确理解了您的需求。

使用Join 根据返回为 next 的 studentId 从 tbl_student 获取学生信息：-

而不是：-

SELECT CASE 
        WHEN(Prev.HighScoreUser <= Cur.HighScoreUser)
        THEN 'Yes'
        ELSE 'No'
        END as HaveGift,Prev.StudentId

FROM Prev
INNER JOIN Cur
ON Prev.StudentId = Cur.StudentId
WHERE Prev.StudentId=@StudentId

类型：

SELECT CASE 
        WHEN(Prev.HighScoreUser <= Cur.HighScoreUser)
        THEN 'Yes'
        ELSE 'No'
        END as HaveGift,Prev.StudentId
        , std.name, std. .... -- put your columns here that refer to student info 

FROM Prev
INNER JOIN Cur
ON Prev.StudentId = Cur.StudentId
INNER JOIN tbl_student  std
    on std.StudentId = Cur.StudentId
WHERE Prev.StudentId=@StudentId

【讨论】：