如何在 SQL Server 2014 中呈现分层数据

Question

I have two tables Company and CompanyRelationShip .

DECLARE @Company TABLE (
    CompanyId INT
    ,RootCompanyId INT
    ,CompanyName VARCHAR(100)
    )

INSERT INTO @Company
VALUES (2,2,'ROOT')
,(106,2,'ABC')
,(105,2,'CDF')
,(3,3,'ROOT2')
,(150,3,'YXZ')
,(151,3,'XZX')


DECLARE @CompanyRelationShip TABLE (
    PrimaryCompanyId INT
    ,CompanyId INT
    )

INSERT INTO @CompanyRelationShip
VALUES (2,2)
,(2,106)
,(2,105)
,(106,105)
,(3,3)
,(3,151)
,(3,150)
,(151,150)

I want the result in the below format

CompanyId   PrimayCompanyId PrimaryCompanyName  RootCompanyId   RootCompanyName
2                 2              ROOT               2               ROOT
106               2              ROOT               2               ROOT
105              106             ABC                2               ROOT
3                 3              ROOT2              3               ROOT2
151              3               ROOT2              3               ROOT2
150              151             XZX                3               ROOT2

I have tried the below query to get the result

WITH PrimayCompany
AS (
    SELECT CR.PrimaryCompanyId
        ,C.CompanyName
    FROM @CompanyRelationShip CR
    JOIN @Company C ON CR.CompanyId = CR.PrimaryCompanyId
    )
    ,RootCompany
AS (
    SELECT RootCompanyId
        ,CompanyName
    FROM @Company
    WHERE CompanyId = RootCompanyId
    )
SELECT C.CompanyId
    ,C.RootCompanyId
    ,RC.CompanyName
    ,CR.PrimaryCompanyId
    ,PC.CompanyName
FROM @Company C
LEFT JOIN @CompanyRelationShip CR ON C.CompanyId = CR.PrimaryCompanyId
LEFT JOIN PrimayCompany PC ON PC.PrimaryCompanyId = CR.PrimaryCompanyId
LEFT JOIN RootCompany RC ON RC.RootCompanyId = CR.PrimaryCompanyId

I would really appreciate a bit of help.

Answer 1

In my comment I asked you, why you would need the table @CompanyRelationShip at all... This is just adding a hell of a lot of complexity and potentials for errors.

My suggestion relies on the first table alone. Look, how I've changed the parent IDs of 105 and 151 to place them below in the hierarchy. Just to show the principles I've added a second child below 150 :

DECLARE @Company TABLE (
    CompanyId INT
    ,RootCompanyId INT
    ,CompanyName VARCHAR(100)
    );

INSERT INTO @Company
VALUES (2,2,'ROOT')
,(106,2,'ABC')
,(105,106,'CDF')
,(3,3,'ROOT2')
,(150,3,'YXZ')
,(151,150,'XZX')
,(152,150,'Second below 150');

--the query

WITH recCTE AS
(
    SELECT CompanyId AS [RootId],CompanyName AS [RootName],*,1 AS HierarchyLevel FROM @Company WHERE CompanyId=RootCompanyId
    UNION ALL
    SELECT rc.RootId,rc.RootName,c.*,rc.HierarchyLevel+1
    FROM @Company c
    INNER JOIN recCTE rc ON c.RootCompanyId=rc.CompanyId AND c.CompanyId<>rc.CompanyId
)
SELECT RootId
      ,RootName
      ,RootCompanyId AS [PrevId]
      ,CompanyId
      ,CompanyName
      ,HierarchyLevel 
FROM recCTE rc
ORDER BY RootId,HierarchyLevel;

The result

RootId  RootName    PrevId  CompanyId   CompanyName     HierarchyLevel
2       ROOT        2       2           ROOT                1
2       ROOT        2       106         ABC                 2
2       ROOT        106     105         CDF                 3
3       ROOT2       3       3           ROOT2               1
3       ROOT2       3       150         YXZ                 2
3       ROOT2       150     151         XZX                 3
3       ROOT2       150     152         Second below 150    3

The idea in short:

• We use aa recursive CTE (which is a rather iterative concept actually).
• The first SELECT (the anchor ) starts with the companies, where the two IDs match.
• The second SELECT after UNION ALL picks the next level by joining to the intermediate result line
• The two columns RootId and RootName are just passed through to show up in your final set.

The HierarchyLevel is the position within the line, thus placing 105 within ROOT, but below 106.

Hope this helps...

A solution for the given structure

As told, the given structure is not the best choice and should be altered. But if you have to stick to this, you might try something along this:

WITH recCTE AS
(
    SELECT CompanyId AS [RootId],CompanyName AS [RootName],*,1 AS HierarchyLevel FROM @Company WHERE CompanyId=RootCompanyId
    UNION ALL
    SELECT rc.RootId,rc.RootName,c.*,rc.HierarchyLevel+1
    FROM @Company c
    INNER JOIN recCTE rc ON c.RootCompanyId=rc.CompanyId AND c.CompanyId<>rc.CompanyId
)
SELECT rc.CompanyId
      ,rc.CompanyName  
      ,COALESCE(crs.PrimaryCompanyId,rc.RootCompanyId) AS ComputedPrevId
      ,COALESCE(c1.CompanyName,rc.RootName) AS ComputedPrevName
      ,rc.RootId
      ,rc.RootName
FROM recCTE rc
LEFT JOIN @CompanyRelationShip  crs ON rc.CompanyId=crs.CompanyId AND rc.RootCompanyId<>crs.PrimaryCompanyId
LEFT JOIN @Company c1 ON crs.PrimaryCompanyId=c1.CompanyId
ORDER BY rc.RootId,rc.HierarchyLevel;

This will first use a recursive CTE to find the children below their root companies and the will try to find the corresponding line in your relationship table.

If you use just SELECT * instead of the column list you can see the full set. Using LEFT JOIN will return NULL , when the ON claus is not met.

COALESCE will return the first non-NULL value, so - hopefully - the one you are after.