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BI SQL # 147 : SQL Server DBA Scripts : Delete rows from relational tables with foreign keys

August 2, 2013 7:00 am

Hi Friends,

In this article we are going to cover How to Delete rows from relational tables with foreign keys.

In this post we are going to discuss following points:

Problem Statement of SQL Script:

Description of SQL Script:

SQL Script Code

SQL Script Output Screenshot

User Level to execute

Problem Statement of SQL Script:

Delete rows from relational tables with foreign keys.

Description of SQL Script:

This T-SQL Script will give the tree structure, so the output of this procedure you can use to delete or insert or update the keys.

SQL Script Code

ALTER PROCEDURE pr_schema
AS
SET NOCOUNT ON

-- 1  
SELECT SCHEMA_NAME(SOF.SCHEMA_ID) AS FSC_NAME
    ,T1.FKEYID AS FK
    ,SCHEMA_NAME(SOR.SCHEMA_ID) AS RSC_NAME
    ,T1.RKEYID AS PK
INTO #sysref
FROM sysforeignkeys T1
LEFT OUTER JOIN sys.objects SOF ON SOF.OBJECT_ID = T1.FKEYID
LEFT OUTER JOIN sys.objects SOR ON SOR.OBJECT_ID = T1.RKEYID
-- below 3 lines is to avoid the problems with self reference  
LEFT OUTER JOIN SYSREFERENCES T2 ON OBJECT_NAME(T1.FKEYID) + 
    OBJECT_NAME(T1.RKEYID) = OBJECT_NAME(T2.RKEYID) + 
    OBJECT_NAME(T2.FKEYID)
WHERE T2.FKEYID IS NULL

--*******************************************************  
-- Get the Max No.Of Joins foreign keys in a Chain  
DECLARE @N VARCHAR(9);

WITH CTE (
    FKEYID
    ,LEVEL
    )
AS (
    SELECT FKEYID
        ,0
    FROM sysforeignkeys
    
    UNION ALL
    
    SELECT T1.PK
        ,LEVEL + 1
    FROM #sysref T1
    JOIN CTE T2 ON T1.FK = T2.FKEYID
    )
-- Statement that executes the CTE 
SELECT @N = Max(LEVEL)
FROM CTE

PRINT @N

--*******************************************************  
DECLARE @V1 VARCHAR(max)

SET @V1 = ''

DECLARE @V2 VARCHAR(max)

SET @V2 = ''

DECLARE @select VARCHAR(max)

SET @select = ''

DECLARE @OrderBy VARCHAR(2)

SET @OrderBy = @N + 1

WHILE NOT @N = 0
BEGIN
    SET @V1 = @V1 + ' right outer join #sysref A' + cast(@N AS 
            VARCHAR(4)) + ' on a' + @V2 + '.pk =A' + cast(@N AS 
            VARCHAR(4)) + '.fk'
    SET @select = @select + 'a' + @N + '.FSC_NAME+''.''+object_name(' 
        + 'a' + @N + '.fk) AS key' + convert(VARCHAR, (@N + 1
                )) + ','
    SET @V2 = @N
    SET @N = @N - 1

    CONTINUE
END

SET @select = @select + 
    'A1.RSC_NAME+''.''+object_name(A1.PK) AS  Key1'

EXEC (
        'SELECT ' + @select + '  from #sysref a ' + @V1 + 
        ' order by ' + @OrderBy
        )

SQL Script Output Screenshot

User Level to execute

400

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Posted by Vishal Pawar

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