Finding Circular Foreign Key References

GetCircularReferences.sql

-- Source: https://blogs.msdn.microsoft.com/appfabricannounce/2010/07/01/finding-circular-foreign-key-references/

SET NOCOUNT ON

-- WWB: Create a Temp Table Of All Relationship To Improve Overall Performance
CREATE TABLE #TableRelationships (FK_Schema nvarchar(max), FK_Table nvarchar(max),
    PK_Schema nvarchar(max), PK_Table nvarchar(max))

-- WWB: Create a List Of All Tables To Check
CREATE TABLE #TableList ([Schema] nvarchar(max), [Table] nvarchar(max))

-- WWB: Fill the Table List
INSERT INTO #TableList ([Table], [Schema])
SELECT TABLE_NAME, TABLE_SCHEMA
FROM INFORMATION_SCHEMA.TABLES 
WHERE Table_Type = 'BASE TABLE'

-- WWB: Fill the RelationShip Temp Table
INSERT INTO #TableRelationships(FK_Schema, FK_Table, PK_Schema, PK_Table)
SELECT
    FK.TABLE_SCHEMA,
    FK.TABLE_NAME,
    PK.TABLE_SCHEMA,
    PK.TABLE_NAME
FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS C
      INNER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS FK ON 
        C.CONSTRAINT_NAME = FK.CONSTRAINT_NAME
      INNER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS PK ON 
        C.UNIQUE_CONSTRAINT_NAME = PK.CONSTRAINT_NAME
      INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE CU ON 
        C.CONSTRAINT_NAME = CU.CONSTRAINT_NAME
      INNER JOIN (
            SELECT i1.TABLE_NAME, i2.COLUMN_NAME
            FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS i1
            INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE i2 ON
             i1.CONSTRAINT_NAME = i2.CONSTRAINT_NAME
            WHERE i1.CONSTRAINT_TYPE = 'PRIMARY KEY'
) PT ON PT.TABLE_NAME = PK.TABLE_NAME

CREATE TABLE #Stack([Schema] nvarchar(max), [Table] nvarchar(max))

GO

-- WWB: Drop SqlAzureRecursiveFind
IF  EXISTS (SELECT * FROM sys.objects WHERE object_id = 
    OBJECT_ID(N'[dbo].[SqlAzureRecursiveFind]') AND type in (N'P', N'PC'))
DROP PROCEDURE [dbo].[SqlAzureRecursiveFind]

GO

-- WWB: Create a Stored Procedure that Recursively Calls Itself
CREATE PROC SqlAzureRecursiveFind
    @BaseSchmea nvarchar(max),
    @BaseTable nvarchar(max),
    @Schmea nvarchar(max),
    @Table nvarchar(max),
    @Fail nvarchar(max) OUTPUT
AS

    SET NOCOUNT ON
              
    -- WWB: Keep Track Of the Schema and Tables We Have Checked
    -- Prevents Looping          
    INSERT INTO #Stack([Schema],[Table]) VALUES (@Schmea, @Table)
    
    DECLARE @RelatedSchema nvarchar(max)
    DECLARE @RelatedTable nvarchar(max)
    
    -- WWB: Select all tables that the input table is dependent on
    DECLARE table_cursor CURSOR LOCAL  FOR
          SELECT PK_Schema, PK_Table
          FROM #TableRelationships
          WHERE FK_Schema = @Schmea AND FK_Table = @Table

    OPEN table_cursor;

    -- Perform the first fetch.
    FETCH NEXT FROM table_cursor INTO @RelatedSchema, @RelatedTable;

    -- Check @@FETCH_STATUS to see if there are any more rows to fetch.
    WHILE @@FETCH_STATUS = 0
    BEGIN
    
        -- WWB: If We have Recurred To Where We Start This
        -- Is a Circular Reference
        -- Begin failing out of the recursions
        IF (@BaseSchmea = @RelatedSchema AND 
                @BaseTable = @RelatedTable)
            BEGIN
                SET @Fail = @RelatedSchema + '.' + @RelatedTable
                RETURN
            END
        ELSE            
        BEGIN
        
            DECLARE @Count int
        
            -- WWB: Check to make sure that the dependencies are not in the stack
            -- If they are we don't need to go down this branch
            SELECT    @Count = COUNT(1)
            FROM    #Stack    
            WHERE    #Stack.[Schema] = @RelatedSchema AND 
                #Stack.[Table] = @RelatedTable
        
            IF (@Count=0) 
            BEGIN
                -- WWB: Recurse
                EXECUTE SqlAzureRecursiveFind @BaseSchmea, 
                    @BaseTable, 
                    @RelatedSchema, @RelatedTable, @Fail OUTPUT
                IF (LEN(@Fail) > 0)
                BEGIN
                    -- WWB: If the Call Fails, Build the Output Up
                    SET @Fail = @RelatedSchema + '.' + @RelatedTable 
                        + ' -> ' + @Fail
                    RETURN
                END
            END
       END
           
       -- This is executed as long as the previous fetch succeeds.
    FETCH NEXT FROM table_cursor INTO @RelatedSchema, @RelatedTable;
    END

    CLOSE table_cursor;
    DEALLOCATE table_cursor;    

GO    

SET NOCOUNT ON

DECLARE @Schema nvarchar(max)
DECLARE @Table nvarchar(max)
DECLARE @Fail nvarchar(max)

-- WWB: Loop Through All the Tables In the Database Checking Each One
DECLARE list_cursor CURSOR FOR
      SELECT [Schema], [Table]
      FROM #TableList

OPEN list_cursor;

-- Perform the first fetch.
FETCH NEXT FROM list_cursor INTO @Schema, @Table;

-- Check @@FETCH_STATUS to see if there are any more rows to fetch.
WHILE @@FETCH_STATUS = 0
BEGIN

    -- WWB: Clear the Stack (Don't you love Global Variables)
    DELETE #Stack
    
    -- WWB: Initialize the Input
    SET @Fail = ''

    -- WWB: Check the Table
    EXECUTE SqlAzureRecursiveFind @Schema, 
        @Table, @Schema,
         @Table, @Fail OUTPUT
    IF (LEN(@Fail) > 0)
    BEGIN
        -- WWB: Failed, Output
        SET @Fail = @Schema + '.' + @Table + ' -> ' + @Fail
        PRINT @Fail
    END
            
   -- This is executed as long as the previous fetch succeeds.
    FETCH NEXT FROM list_cursor INTO @Schema, @Table;
END

-- WWB: Clean Up
CLOSE list_cursor;
DEALLOCATE list_cursor;    
                    
DROP TABLE #TableRelationships
DROP TABLE #Stack
DROP TABLE #TableList
DROP PROC SqlAzureRecursiveFind