在一列连接多个行

Question

我有产生以下结果

NAME   WeekPattern 

John Smith 
John Smith // 
John Smith OO 
Jack Jones 
Jack Jones O 
Jack Jones // 

查询有没有一种方法我可以连接的WeekPattern列，这样的结果将显示如下：

NAME   WeekPattern 

John Smith  // OO 
Jack Jones  O // 

我曾尝试使用FOR XML PATH但无法使其正常工作，下面是查询我的尝试：

SELECT 
p.p_surname, 
p.p_forenames, 
LEFT(sr.sr_weekpattern , LEN(sr.sr_weekpattern)-1) AS Weekpattern 
FROM 
unitesnapshot.dbo.capd_studentregister sr 
INNER JOIN unitesnapshot.dbo.capd_person p ON p.p_id = sr.sr_student 
CROSS APPLY 
(
    SELECT sr.sr_weekpattern + ' ' 
    FROM unitesnapshot.dbo.capd_studentregister sr1 
    INNER JOIN unitesnapshot.dbo.capd_person p1 ON p1.p_id = sr1.sr_student 

    WHERE p.p_id = p1.p_id 
    FOR XML PATH('') 
) pre_trimmed (Weekpattern) 
GROUP BY p.p_surname, p.p_forenames, sr.sr_weekpattern; 

运行此查询时出现此错误：

传递给LEFT或SUBSTRING函数的长度参数无效。

任何帮助会根据您现有的查询非常感激

Answer 1

，你是不是在LEFT引用正确的列，你应该用：

SELECT 
    p.p_surname, 
    p.p_forenames, 
    LEFT(pre_trimmed.Weekpattern , LEN(pre_trimmed.Weekpattern)-1) AS Weekpattern 
FROM unitesnapshot.dbo.capd_studentregister sr 
INNER JOIN unitesnapshot.dbo.capd_person p 
    ON p.p_id = sr.sr_student 
CROSS APPLY 
(
    SELECT sr1.sr_weekpattern + ' ' 
    FROM unitesnapshot.dbo.capd_studentregister sr1 
    INNER JOIN unitesnapshot.dbo.capd_person p1 
    ON p1.p_id = sr1.sr_student 
    WHERE p.p_id = p1.p_id 
    FOR XML PATH('') 
) pre_trimmed (Weekpattern) 

Answer 2

SELECT 
    Name, 
    STUFF(
     (SELECT ' ' + WeekPattern 
      FROM TableName 
      WHERE NAME = a.NAME AND WeekPattern IS NOT NULL 
      FOR XML PATH ('')) 
      , 1, 1, '') AS WeekPatternList 
FROM TableName AS a 
GROUP BY Name 

• SQLFiddle Demo