按 XML 个不同的案例排序

Question

SQL Server 2012 架构设置：

CREATE TABLE Course
(
     CourseID INT IDENTITY(1,1)
    ,CourseName NVARCHAR(20)
)

CREATE TABLE Session
(
     SessionID INT IDENTITY(1,1)
    ,CourseID  INT NULL
)

CREATE TABLE SessionTime
(
    ,SessionID INT
    ,DayOfWeek TINYINT --Sunday(0), Monday(1), ..., Saturday(6)
)

INSERT INTO COURSE(CourseName) VALUES('Science 10'), ('Bio 30')
INSERT INTO Session(CourseID) VALUES(1), (2)

INSERT INTO SessionTime(SessionID, DayOfWeek)
VALUES(1, 5), (1, 0), (1, 0), (1, 0), (1, 2), (1, 2), (1, 4),
      (2, 1), (2, 3)

查询：

SELECT   C.CourseName
        ,S.SessionID
        ,STUFF(
                (SELECT DISTINCT ', ' + CASE 
                                            WHEN ST.DayOfWeek = 0 THEN 'Su'
                                            WHEN ST.DayOfWeek = 1 THEN 'M'
                                            WHEN ST.DayOfWeek = 2 THEN 'T'
                                            WHEN ST.DayOfWeek = 3 THEN 'W'
                                            WHEN ST.DayOfWeek = 4 THEN 'Th'
                                            WHEN ST.DayOfWeek = 5 THEN 'F'
                                            WHEN ST.DayOfWeek = 6 THEN 'Sa'
                                        END
                FROM SessionTime ST
                WHERE ST.SessionID = S.SessionID
                --ORDER BY DayOfWeek
                FOR XML PATH (''))
            ,1,2,'') AS DaysOfWeek
FROM Session S
INNER JOIN Course C on S.CourseID = C.CourseID

Results:

| COURSENAME | SESSIONID |   DAYSOFWEEK |
|------------|-----------|--------------|
| Science 10 |         1 | F, Su, T, Th |
|     Bio 30 |         2 |         M, W |

想要的结果：

| COURSENAME | SESSIONID |   DAYSOFWEEK |
|------------|-----------|--------------|
| Science 10 |         1 | Su, T, Th, F | *Order of DaysOfWeek has changed.
|     Bio 30 |         2 |         M, W |

我想先订购 DayOfWeek (Su,M,T,W,Th,F,Sa) STUFF 但我的尝试导致了以下错误：

ORDER BY items must appear in the select list if SELECT DISTINCT is specified.

我试过以下方法：

ORDER BY 1 不按字母顺序排列日期 (Su,M,T,W,Th,F,Sa)
ORDER BY DayOfWeek 导致上述错误消息
ORDER BY DayOfWeekCase 将 AS DayOfWeekCase 添加到 CASE 的 END 但这改变了 FOR XML returns days

如何在 STUFF 合并之前订购 DayOfWeek？

谢谢！

Answer 1

不要使用 DISTINCT，请尝试使用 GROUP BY。然后，你可以做 ORDER BY DayOfWeek.

SELECT   C.CourseName
        ,S.SessionID
        ,STUFF(
                (SELECT ', ' + CASE 
                                            WHEN ST.DayOfWeek = 0 THEN 'Su'
                                            WHEN ST.DayOfWeek = 1 THEN 'M'
                                            WHEN ST.DayOfWeek = 2 THEN 'T'
                                            WHEN ST.DayOfWeek = 3 THEN 'W'
                                            WHEN ST.DayOfWeek = 4 THEN 'Th'
                                            WHEN ST.DayOfWeek = 5 THEN 'F'
                                            WHEN ST.DayOfWeek = 6 THEN 'Sa'
                                        END
                FROM SessionTime ST
                WHERE ST.SessionID = S.SessionID
                GROUP BY st.DayOfWeek
                ORDER BY DayOfWeek              
                FOR XML PATH (''))
            ,1,2,'') AS DaysOfWeek
FROM Session S
INNER JOIN Course C on S.CourseID = C.CourseID

按 XML 个不同的案例排序

ORDER BY DISTINCT CASE FOR XML

sql

sql-server

sql-order-by

distinct