SQL Script to alter ALL Foreign Keys to add ON DELETE CASCADE

Question

I have a SQL 2005 database with approx 250 tables.

I want to temporarily enable ON DELETE CASCADE to all of the Foreign Keys so that I can do a bulk delete easily.

Answer 1

More Standards compliant solution:

;WITH CTE AS 
(
    SELECT  
         KCU1.CONSTRAINT_NAME AS FK_CONSTRAINT_NAME 
        ,KCU1.TABLE_SCHEMA AS FK_SCHEMA_NAME 
        ,KCU1.TABLE_NAME AS FK_TABLE_NAME 
        ,KCU1.COLUMN_NAME AS FK_COLUMN_NAME 
        ,KCU1.ORDINAL_POSITION AS FK_ORDINAL_POSITION 
        ,KCU2.CONSTRAINT_NAME AS REFERENCED_CONSTRAINT_NAME 
        ,KCU2.TABLE_SCHEMA AS REFERENCED_SCHEMA_NAME 
        ,KCU2.TABLE_NAME AS REFERENCED_TABLE_NAME 
        ,KCU2.COLUMN_NAME AS REFERENCED_COLUMN_NAME 
        ,KCU2.ORDINAL_POSITION AS REFERENCED_ORDINAL_POSITION 
    FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS RC 

    INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE KCU1 
        ON KCU1.CONSTRAINT_CATALOG = RC.CONSTRAINT_CATALOG  
        AND KCU1.CONSTRAINT_SCHEMA = RC.CONSTRAINT_SCHEMA 
        AND KCU1.CONSTRAINT_NAME = RC.CONSTRAINT_NAME 

    INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE KCU2 
        ON KCU2.CONSTRAINT_CATALOG = RC.UNIQUE_CONSTRAINT_CATALOG  
        AND KCU2.CONSTRAINT_SCHEMA = RC.UNIQUE_CONSTRAINT_SCHEMA 
        AND KCU2.CONSTRAINT_NAME = RC.UNIQUE_CONSTRAINT_NAME 
        AND KCU2.ORDINAL_POSITION = KCU1.ORDINAL_POSITION 
)


SELECT 
     FK_CONSTRAINT_NAME
    --,FK_SCHEMA_NAME
    --,FK_TABLE_NAME
    --,FK_COLUMN_NAME
    --,FK_ORDINAL_POSITION
    --,REFERENCED_CONSTRAINT_NAME
    --,REFERENCED_SCHEMA_NAME
    --,REFERENCED_TABLE_NAME
    --,REFERENCED_COLUMN_NAME
    --,REFERENCED_ORDINAL_POSITION

    ,
        'ALTER TABLE [' + FK_SCHEMA_NAME + ']' 
        + '.[' + FK_TABLE_NAME + '] ' 
        + 'DROP CONSTRAINT [' + FK_CONSTRAINT_NAME + ']; ' 
    AS DropStmt 

    ,
    'ALTER TABLE [' + FK_SCHEMA_NAME + ']' 
        + '.[' + FK_TABLE_NAME + '] ' + 
        + 'WITH CHECK ADD CONSTRAINT [' +  FK_CONSTRAINT_NAME + '] ' 
        + 'FOREIGN KEY([' + FK_COLUMN_NAME + ']) ' 
        + 'REFERENCES [' + REFERENCED_SCHEMA_NAME + '].[' + REFERENCED_TABLE_NAME + ']([' + REFERENCED_COLUMN_NAME + ']) ON DELETE CASCADE; ' 
    AS CreateStmt 

FROM CTE 

WHERE (1=1) 
/*
AND FK_TABLE_NAME IN 
(
     'T_SYS_Geschossrechte'
    ,'T_SYS_Gebaeuderechte'
    ,'T_SYS_Standortrechte'
)

AND REFERENCED_TABLE_NAME NOT LIKE 'T_AP_Ref_Mandant'
*/

ORDER BY  
     FK_TABLE_NAME
    ,FK_CONSTRAINT_NAME
    ,FK_COLUMN_NAME
    ,FK_ORDINAL_POSITION
    ,REFERENCED_CONSTRAINT_NAME
    ,REFERENCED_TABLE_NAME
    ,REFERENCED_COLUMN_NAME
    ,REFERENCED_ORDINAL_POSITION

Edit:
Extended for multi-column foreign-keys:

;WITH CTE AS 
( 
  SELECT  
         KCU1.CONSTRAINT_NAME AS FK_CONSTRAINT_NAME 
        ,KCU1.TABLE_SCHEMA AS FK_SCHEMA_NAME 
        ,KCU1.TABLE_NAME AS FK_TABLE_NAME 
        ,KCU1.COLUMN_NAME AS FK_COLUMN_NAME 
        ,KCU1.ORDINAL_POSITION AS FK_ORDINAL_POSITION 
        ,KCU2.CONSTRAINT_NAME AS REFERENCED_CONSTRAINT_NAME 
        ,KCU2.TABLE_SCHEMA AS REFERENCED_SCHEMA_NAME 
        ,KCU2.TABLE_NAME AS REFERENCED_TABLE_NAME 
        ,KCU2.COLUMN_NAME AS REFERENCED_COLUMN_NAME 
        ,KCU2.ORDINAL_POSITION AS REFERENCED_ORDINAL_POSITION 
    FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS RC 

    INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE KCU1 
        ON KCU1.CONSTRAINT_CATALOG = RC.CONSTRAINT_CATALOG  
        AND KCU1.CONSTRAINT_SCHEMA = RC.CONSTRAINT_SCHEMA 
        AND KCU1.CONSTRAINT_NAME = RC.CONSTRAINT_NAME 

    INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE KCU2 
        ON KCU2.CONSTRAINT_CATALOG = RC.UNIQUE_CONSTRAINT_CATALOG  
        AND KCU2.CONSTRAINT_SCHEMA = RC.UNIQUE_CONSTRAINT_SCHEMA 
        AND KCU2.CONSTRAINT_NAME = RC.UNIQUE_CONSTRAINT_NAME 
        AND KCU2.ORDINAL_POSITION = KCU1.ORDINAL_POSITION 
)
SELECT 
     FK_SCHEMA_NAME
    ,FK_TABLE_NAME
    ,FK_CONSTRAINT_NAME 
    --,FK_COLUMN_NAME
    --,REFERENCED_COLUMN_NAME



    ,
    'ALTER TABLE ' + QUOTENAME(FK_SCHEMA_NAME) + '.' + QUOTENAME(FK_TABLE_NAME) + ' ' 
      + 'DROP CONSTRAINT ' + QUOTENAME(FK_CONSTRAINT_NAME) + '; ' 
    AS DropStmt 

    ,
    'ALTER TABLE ' + QUOTENAME(FK_SCHEMA_NAME) + '.' + QUOTENAME(FK_TABLE_NAME) + ' 
    ADD CONSTRAINT ' + QUOTENAME(FK_CONSTRAINT_NAME) + ' 
    FOREIGN KEY('
    + 
        SUBSTRING 
        ( 
            (
                SELECT ', ' + QUOTENAME(FK.FK_COLUMN_NAME) AS [text()] 
                FROM CTE AS FK 
                WHERE FK.FK_CONSTRAINT_NAME = CTE.FK_CONSTRAINT_NAME
                AND FK.FK_SCHEMA_NAME = CTE.FK_SCHEMA_NAME
                AND FK.FK_TABLE_NAME = CTE.FK_TABLE_NAME 
                ORDER BY FK.FK_ORDINAL_POSITION
                FOR XML PATH, TYPE 
            ).value('.[1]', 'nvarchar(MAX)')
            ,3, 4000
        ) 
    + ') 
'
    + '    REFERENCES ' + QUOTENAME(REFERENCED_SCHEMA_NAME) + '.' + QUOTENAME(REFERENCED_TABLE_NAME) + '(' 
    + SUBSTRING 
      ( 
          (
              SELECT ', ' + QUOTENAME(Referenced.REFERENCED_COLUMN_NAME) AS [text()] 
              FROM CTE AS Referenced 
              WHERE Referenced.FK_CONSTRAINT_NAME = CTE.FK_CONSTRAINT_NAME
              AND Referenced.REFERENCED_SCHEMA_NAME = CTE.REFERENCED_SCHEMA_NAME
              AND Referenced.REFERENCED_TABLE_NAME = CTE.REFERENCED_TABLE_NAME
              ORDER BY Referenced.REFERENCED_ORDINAL_POSITION 
              FOR XML PATH, TYPE 
          ).value('.[1]', 'nvarchar(MAX)')
          , 3, 4000 
      )
    + ') 
    ON DELETE CASCADE 
; ' AS CreateStmt 

FROM CTE 

GROUP BY 
     FK_SCHEMA_NAME
    ,FK_TABLE_NAME
    ,FK_CONSTRAINT_NAME 

    ,REFERENCED_SCHEMA_NAME
    ,REFERENCED_TABLE_NAME

And the far simpler version for PostGreSQL:

;WITH CTE AS 
( 
  SELECT  
         KCU1.CONSTRAINT_NAME AS FK_CONSTRAINT_NAME 
        ,KCU1.TABLE_SCHEMA AS FK_SCHEMA_NAME 
        ,KCU1.TABLE_NAME AS FK_TABLE_NAME 
        ,KCU1.COLUMN_NAME AS FK_COLUMN_NAME 
        ,KCU1.ORDINAL_POSITION AS FK_ORDINAL_POSITION 
        ,KCU2.CONSTRAINT_NAME AS REFERENCED_CONSTRAINT_NAME 
        ,KCU2.TABLE_SCHEMA AS REFERENCED_SCHEMA_NAME 
        ,KCU2.TABLE_NAME AS REFERENCED_TABLE_NAME 
        ,KCU2.COLUMN_NAME AS REFERENCED_COLUMN_NAME 
        ,KCU2.ORDINAL_POSITION AS REFERENCED_ORDINAL_POSITION 
    FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS RC 

    INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE KCU1 
        ON KCU1.CONSTRAINT_CATALOG = RC.CONSTRAINT_CATALOG  
        AND KCU1.CONSTRAINT_SCHEMA = RC.CONSTRAINT_SCHEMA 
        AND KCU1.CONSTRAINT_NAME = RC.CONSTRAINT_NAME 

    INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE KCU2 
        ON KCU2.CONSTRAINT_CATALOG = RC.UNIQUE_CONSTRAINT_CATALOG  
        AND KCU2.CONSTRAINT_SCHEMA = RC.UNIQUE_CONSTRAINT_SCHEMA 
        AND KCU2.CONSTRAINT_NAME = RC.UNIQUE_CONSTRAINT_NAME 
        AND KCU2.ORDINAL_POSITION = KCU1.ORDINAL_POSITION 
)
SELECT 
     FK_SCHEMA_NAME
    ,FK_TABLE_NAME
    ,FK_CONSTRAINT_NAME 
    --,FK_COLUMN_NAME
    --,REFERENCED_COLUMN_NAME



    ,
    'ALTER TABLE ' || QUOTE_IDENT(FK_SCHEMA_NAME) || '.' || QUOTE_IDENT(FK_TABLE_NAME) || ' ' 
      || 'DROP CONSTRAINT ' || QUOTE_IDENT(FK_CONSTRAINT_NAME) || '; ' 
    AS DropStmt 

    ,
    'ALTER TABLE ' || QUOTE_IDENT(FK_SCHEMA_NAME) || '.' || QUOTE_IDENT(FK_TABLE_NAME) || ' 
    ADD CONSTRAINT ' || QUOTE_IDENT(FK_CONSTRAINT_NAME) || ' 
    FOREIGN KEY(' || string_agg(FK_COLUMN_NAME, ', ') || ') 
'
    || '    REFERENCES ' || QUOTE_IDENT(REFERENCED_SCHEMA_NAME) || '.' || QUOTE_IDENT(REFERENCED_TABLE_NAME) || '(' || string_agg(REFERENCED_COLUMN_NAME, ', ') || ') 
    ON DELETE CASCADE 
; ' AS CreateStmt 

FROM CTE 

GROUP BY 
     FK_SCHEMA_NAME
    ,FK_TABLE_NAME
    ,FK_CONSTRAINT_NAME 

    ,REFERENCED_SCHEMA_NAME
    ,REFERENCED_TABLE_NAME