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SQL Server: How can I SELECT FROM TABLE TO Other Format?

开发者 https://www.devze.com 2022-12-23 17:29 出处:网络
I have Table A. How can I select from Table A to get Table B Format? Table A Employee Name Effective Date FieldTypeFieldValue

I have Table A. How can I select from Table A to get Table B Format?

Table A

Employee Name Effective Date FieldType     FieldValue
Maung Mya           1/1/2005 Title         Project Engineer
Maung Mya           1/1/2005 Department    IT Department
Maung Mya           1/1/2007 Title         开发者_运维问答Assist Project Manager
Kyaw Kyaw           1/1/2006 Title         Software Engineer
Kyaw Kyaw           1/1/2006 Department    IT Department

Table B

Effective Date Employee Name Title                  Department
1/1/2007       Maung Mya     Assist Project Manager IT Department
1/1/2006       Kyaw Kyaw     Software Engineer      IT Department


It looks like you want something like this:

SELECT A.[Effective Date],
       A.[Employee Name],
       A.FieldValue AS Title,
       A2.FieldValue AS Department
FROM A INNER JOIN
     A AS A2
     ON A.[Employee Name] = A2.[Employee Name] AND
        A.[Effective Date] = A2.[Effective Date] AND
        A.FieldType = 'Title' AND
        A2.FieldType = 'Department'
WHERE A.[Effective Date] = (
    SELECT MAX([Effective Date])
    FROM A AS A3
    WHERE A3.[Employee Name] = A.[Employee Name] AND A3.FieldType = 'Title')
    AND A2.[Effective Date] = (
    SELECT MAX([Effective Date])
    FROM A AS A4
    WHERE A4.[Employee Name] = A2.[Employee Name] AND A3.FieldType = 'Department')


EDIT: RedsDevils I have edited my code and tested it using your example. This should work now

Bearing in mind that the same employee might change department, or get a promotion through his career, my two joins look for the latest Effective Date for each type.

SELECT  derived.[Effective Date], 
        derived.[Employee Name],
        title1.[FieldValue] AS Title, 
        dept1.[FieldValue] AS Department
FROM 
    (
        SELECT MAX([Effective Date]) AS [Effective Date], [Employee Name] 
        FROM TableA
        GROUP BY [Employee Name] 
    ) derived

    -- Inner Join for TITLE
    INNER JOIN TableA title1 ON derived.[Employee Name] = title1.[Employee Name]
    AND title1.FieldType = 'Title'
    AND title1.[Effective Date] = (SELECT MAX(title2.[Effective Date]) 
                                FROM TableA title2 
                                WHERE title1.[Employee Name] = title2.[Employee Name] 
                                AND title2.FieldType = 'Title') 

    -- Inner Join for DEPARTMENT
    INNER JOIN TableA dept1 ON derived.[Employee Name] = dept1.[Employee Name]
    AND dept1.FieldType = 'Department'
    AND dept1.[Effective Date] = (SELECT MAX(dept2.[Effective Date]) 
                                FROM TableA dept2 
                                WHERE dept1.[Employee Name] = dept2.[Employee Name] 
                                AND dept2.FieldType = 'Department') 

I created a derived table first to get the MAX Effective Date and Employee Name, and aliases it with the name 'derived'. I then created to join to get the last know Title and Department.


Yes, I got it! Based on Gabe's answer, I can retrieve the format I want and only 2 records. Thanks all! The answer is as follows.

SELECT  TableA.[Effective Date],  TableA.[Employee Name],  TableA.FieldValue AS Title,A2.FieldValue AS Department FROM TableA INNER JOIN  TableA AS A2 ON TableA.[EmployeeName] = A2.[EmployeeName] AND  TableA.[EffectiveDate] = (SELECT MAX([EffectiveDate]) FROM TableA AS A3 WHERE A3.[EmployeeName] = TableA.[EmployeeName] AND A3.FieldType = 'Title') AND  TableA.FieldType = 'Title' AND  A2.FieldType = 'Department'
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