编写查询以获取 SQL 中的分层数据

Question

我正在使用MS SQL 2008 R2，我想根据员工检索数据按照所需输出部分中给出的最旧到最新数据的层次结构顺序

我的Table数据如下：

SELECT * FROM 
(
    SELECT Code = 1  ,ParentCode = NULL, EmployeeName  = 'Hemant'
    UNION ALL
    SELECT Code = 2  ,ParentCode = 1, EmployeeName  = 'Sachin'
    UNION ALL
    SELECT Code = 3  ,ParentCode = 2, EmployeeName  = 'Shanti'
    UNION ALL
    SELECT Code = 4  ,ParentCode = 1, EmployeeName  = 'Sandesh'
    UNION ALL
    SELECT Code =  5  ,ParentCode = 3, EmployeeName  = 'Sandeep'
    UNION ALL
    SELECT Code = 6  ,ParentCode = NULL, EmployeeName  = 'Smily'
    UNION ALL
    SELECT Code = 7  ,ParentCode = 6, EmployeeName  = 'Snehi'
    UNION ALL
    SELECT Code =  8  ,ParentCode = 6, EmployeeName  = 'Kiran'
    UNION ALL
    SELECT Code =  9  ,ParentCode = 7, EmployeeName  = 'Shital'
    UNION ALL
    SELECT Code =  10  ,ParentCode = 9, EmployeeName  = 'Simran'
) X

所需输出：

Code    Name        ParentCode   Parent
1      Hemant       NULL         NULL
2      Sachin       1            Hemant
3      Shanti       2            Sachin
5      Sandeep      3            shanti
4      Sandesh      1            Hemant
6      Smily        NULL         NULL
7      Snehi        6            Smily
9      Shital       7            Snehi
10     Simran       9            Shital
8      Kiran        6            Smily

Answer 1

您可以使用 LEFT JOIN:

SELECT t1.Code,
       t1.EmployeeName Name,
       t1.ParentCode,
       t2.EmployeeName Parent
FROM yourTable t1
LEFT JOIN yourTable t2 ON t1.ParentCode = t2.Code

Answer 2

我使用临时 table 首先存储您的 "select union" 数据，然后使用左连接查询数据：

SELECT * 
INTO #temp_tbl_test 
FROM (SELECT Code = 1  ,ParentCode = NULL, EmployeeName  = 'Hemant'
    UNION ALL
    SELECT Code = 2  ,ParentCode = 1, EmployeeName  = 'Sachin'
    UNION ALL
    SELECT Code = 3  ,ParentCode = 2, EmployeeName  = 'Shanti'
    UNION ALL
    SELECT Code = 4  ,ParentCode = 1, EmployeeName  = 'Sandesh'
    UNION ALL
    SELECT Code =  5  ,ParentCode = 3, EmployeeName  = 'Sandeep'
    UNION ALL
    SELECT Code = 6  ,ParentCode = NULL, EmployeeName  = 'Smily'
    UNION ALL
    SELECT Code = 7  ,ParentCode = 6, EmployeeName  = 'Snehi'
    UNION ALL
    SELECT Code =  8  ,ParentCode = 6, EmployeeName  = 'Kiran'
    UNION ALL
    SELECT Code =  9  ,ParentCode = 7, EmployeeName  = 'Shital'
    UNION ALL
    SELECT Code =  10  ,ParentCode = 9, EmployeeName  = 'Simran') x

SELECT base.Code, base.EmployeeName, parent.Code AS ParentCode, parent.EmployeeName AS ParentName
FROM #temp_tbl_test base
LEFT JOIN #temp_tbl_test parent 
ON parent.Code = base.ParentCode

Answer 3

您也可以使用 UNION ALL 和 INNER JOIN 实现相同的输出，如下所示。我已将您的 table 命名为示例数据

SELECT * FROM 
(SELECT code,EmployeeName as Name,Parentcode,NULL AS EmployeeName
FROM SampleData WHERE Parentcode IS NULL
UNION ALL
SELECT s1.code,s1.EmployeeName as Name,s1.ParentCode,s2.EmployeeName
FROM SampleData s1
JOIN SampleData s2 ON s1.parentcode = s2.Code) X
ORDER BY X.code

Answer 4

Use Recusrion for this purpose
SELECT * INTO EmployeeDetails FROM 
(
    SELECT Code = 1  ,ParentCode = NULL, EmployeeName  = 'Hemant'
    UNION ALL
    SELECT Code = 2  ,ParentCode = 1, EmployeeName  = 'Sachin'
    UNION ALL
    SELECT Code = 3  ,ParentCode = 2, EmployeeName  = 'Shanti'
    UNION ALL
    SELECT Code = 4  ,ParentCode = 1, EmployeeName  = 'Sandesh'
    UNION ALL
    SELECT Code =  5  ,ParentCode = 3, EmployeeName  = 'Sandeep'
    UNION ALL
    SELECT Code = 6  ,ParentCode = NULL, EmployeeName  = 'Smily'
    UNION ALL
    SELECT Code = 7  ,ParentCode = 6, EmployeeName  = 'Snehi'
    UNION ALL
    SELECT Code =  8  ,ParentCode = 6, EmployeeName  = 'Kiran'
    UNION ALL
    SELECT Code =  9  ,ParentCode = 7, EmployeeName  = 'Shital'
    UNION ALL
    SELECT Code =  10  ,ParentCode = 9, EmployeeName  = 'Simran'
) X

//这是CTE

WITH REC
(Code,ParentValue,EmployeeName,Parent,Level,GRP,LEVELs,[ORDER])
AS
(
SELECT Code,ParentCode ParentValue,EmployeeName,CONVERT(VARCHAR(max),Null) Parent,
1 level ,Code GRP,STR(0) LEVELs,
CAST(ROW_NUMBER()OVER(PARTITION BY ParentCode ORDER BY ParentCode) AS VARCHAR(MAX)) as [ORDER]
FROM EmployeeDetails WHERE ParentCode is null
UNION ALL
SELECT B.Code,b.ParentCode ParentValue,b.EmployeeName,CONVERT(VARCHAR(max),A.EmployeeName) Parent,
 A.level + 1 Level , A.GRP,STR(ROW_NUMBER() OVER(PArtition By B.ParentCode order by B.ParentCode)) LEVELs,
[ORDER] + CAST(ROW_NUMBER()OVER(PARTITION BY B.ParentCode ORDER BY B.ParentCode) AS VARCHAR(MAX)) AS [ORDER]
FROM EmployeeDetails  B 
INNER JOIN REC A ON B.ParentCode = A.Code
)
SELECT*
FROM REC A
ORDER BY A.[ORDER]

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