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 |

期望的结果：

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

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

如果指定了SELECT DISTINCT，则ORDER BY项必须出现在选择列表中。

我尝试过以下方法：

ORDER BY 1按字母顺序排列日期（Su，M，T，W，Th，F，Sa）
ORDER BY DayOfWeek会产生上述错误消息
ORDER BY DayOfWeekCase将AS DayOfWeekCase添加到END的{{1}}，但会改变CASE返回日期的方式

如何在FOR XML之前订购DayOfWeek？

谢谢！

Answer 1

请尝试使用DISTINCT，而不要使用GROUP BY。然后，您可以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

用于XML的DISTINCT案例订购

1 个答案: