使用FOR XML PATH實現多行數據合併成一列

　　有時爲避免循環操做數據庫、列表展現等一些緣由須要將數據及關聯數據批量加載進行集中處理，一種解決辦法能夠使用FOR XML PATH將多行數據合併成一列，達到字段拼接的效果。例若有兩個表，

　　部門表T_Dept：

　　

　　員工表T_Emp：

　　

　　須要查詢每一個部門下的員工姓名，查詢語句：

 1 SELECT ROW_NUMBER() OVER (ORDER BY DeptId) AS Row, DeptName
 2     , LEFT(A.EmpName, LEN(A.EmpName) - 1) AS EmpName
 3 FROM (
 4     SELECT DeptId, EmpName = (
 5             SELECT EmpName + ','
 6             FROM T_Emp emp2
 7             WHERE emp2.DeptId = emp1.DeptId
 8             FOR XML PATH('')
 9         )
10     FROM T_Emp emp1
11     GROUP BY emp1.DeptId
12 ) A
13     LEFT JOIN T_Dept dept ON dept.Id = A.DeptId

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　　結果集：

 

 

　　也能夠這樣寫：

 1 SELECT ROW_NUMBER() OVER (ORDER BY Id) AS Row, DeptName
 2     , LEFT(A.EmpName, LEN(A.EmpName) - 1) AS EmpName
 3 FROM (
 4     SELECT Id, DeptName, EmpName = (
 5             SELECT EmpName + ','
 6             FROM T_Emp emp1
 7             WHERE emp1.DeptId = dept.Id
 8             FOR XML PATH('')
 9         )
10     FROM T_Dept dept
11 ) A

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　　結果集:

　　

 

 

　　SQL腳本：

 1 CREATE TABLE [dbo].[T_Dept](
 2 
 3     [Id] [int] IDENTITY(1,1) NOT NULL,
 4 
 5     [DeptName] [nvarchar](10) NULL,
 6 
 7  CONSTRAINT [PK_T_Dept] PRIMARY KEY CLUSTERED
 8 
 9 (
10 
11     [Id] ASC
12 
13 )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
14 
15 ) ON [PRIMARY]
16 
17 GO
18 
19  
20 
21 CREATE TABLE [dbo].[T_Emp](
22 
23     [Id] [int] IDENTITY(1,1) NOT NULL,
24 
25     [DeptId] [int] NULL,
26 
27     [EmpName] [nvarchar](10) NULL,
28 
29  CONSTRAINT [PK_T_Emp_1] PRIMARY KEY CLUSTERED
30 
31 (
32 
33     [Id] ASC
34 
35 )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
36 
37 ) ON [PRIMARY]
38 
39 GO
40 
41  
42 
43 ALTER TABLE [dbo].[T_Emp]  WITH CHECK ADD  CONSTRAINT [FK_T_Emp_T_Dept] FOREIGN KEY([DeptId])
44 
45 REFERENCES [dbo].[T_Dept] ([Id])
46 
47 GO
48 
49  
50 
51 ALTER TABLE [dbo].[T_Emp] CHECK CONSTRAINT [FK_T_Emp_T_Dept]
52 
53 GO
54 
55  
56 
57 INSERT INTO [dbo].[T_Dept]
58 SELECT '銷售部'
59 UNION ALL
60 SELECT '研發部'
61 UNION ALL
62 SELECT '人力資源部'
63 UNION ALL
64 SELECT '行政部'
65 UNION ALL
66 SELECT '財務部'
67 
68  
69 
70 INSERT INTO [dbo].[T_Emp]
71 SELECT '1', 'Tom'
72 UNION ALL
73 SELECT '1', 'John'
74 UNION ALL
75 SELECT '2', 'Blue'
76 UNION ALL
77 SELECT '2', 'Banks'
78 UNION ALL
79 SELECT '3', 'Niki'
80 UNION ALL
81 SELECT '3', 'Yuki'
82 UNION ALL
83 SELECT '5', '小明'

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