SQL Server含逗号分隔的数据匹配维表

日常有时候导出数据需求时，数据列会遇到带有分隔符的ID，但又需要匹配维表（如下图所示）将ID变成名称。

这种情况可以采用“分隔-匹配-合并”的方法

具体代码为：

-- 准备工作1：创建事实表数据
CREATE TABLE #StudentSubject
(
StuID INT IDENTITY(1,1) NOT NULL,
StuSubject VARCHAR(500) NOT NULL
)
INSERT INTO #StudentSubject(StuSubject) VALUES ('')
INSERT INTO #StudentSubject(StuSubject) VALUES ('')
INSERT INTO #StudentSubject(StuSubject) VALUES ('2,3')
INSERT INTO #StudentSubject(StuSubject) VALUES ('2,3,4')
INSERT INTO #StudentSubject(StuSubject) VALUES ('1,2,3,4')
INSERT INTO #StudentSubject(StuSubject) VALUES ('')

-- 准备工作2：创建维表数据
CREATE TABLE #D_Subject
(
SubjectID INT IDENTITY(1,1) NOT NULL,
SubjectName VARCHAR(500) NOT NULL
)

INSERT INTO #D_Subject(SubjectName) VALUES ('语文')
INSERT INTO #D_Subject(SubjectName) VALUES ('数学')
INSERT INTO #D_Subject(SubjectName) VALUES ('英语')
INSERT INTO #D_Subject(SubjectName) VALUES ('体育')

SELECT * FROM #StudentSubject
SELECT * FROM #D_Subject
;

-- 1分离：将逗号分隔的StuSubject分离匹配StudentSubject获取标签
WITH CetSubject AS
(
SELECT StuID,
       CAST(LEFT(StuSubject, CHARINDEX(',', StuSubject + ',') - 1) AS NVARCHAR(100)) SubjectID,
       CAST(STUFF(StuSubject + ',', 1, CHARINDEX(',', StuSubject + ','), '') AS NVARCHAR(100)) Split
  FROM #StudentSubject
 UNION ALL
SELECT StuID,
       CAST(LEFT(Split, CHARINDEX(',', Split) - 1) AS NVARCHAR(100)) SIds,
       CAST(STUFF(Split, 1, CHARINDEX(',', Split), '') AS NVARCHAR(100)) Split
  FROM CetSubject
 WHERE split > ''
)
-- 2匹配 将分离后的数据逐行与维表匹配
SELECT CS.StuID,
       DS.SubjectName
  INTO #CetSubjectName
  FROM CetSubject CS
  LEFT JOIN #D_Subject DS ON DS.SubjectID = CS.SubjectID
 WHERE CS.SubjectID <> ''
OPTION (MAXRECURSION 0);

-- 3合并 将与维表匹配的结果用逗号分隔合并还原
SELECT StuID,
       STUFF((SELECT ',' + T.SubjectName FROM #CetSubjectName T WHERE T.StuID = T2.StuID FOR XML PATH('')),1,1,'') SubjectName
  FROM #CetSubjectName t2
 GROUP BY StuID

DROP TABLE #D_Subject
DROP TABLE #StudentSubject
DROP TABLE #CetSubjectName