Generate Delete Statement From Foreign Key Relationships in SQL 2008? - sql

Question

Is it possible via script/tool to generate a delete statement based on the tables fk relations.
i.e. I have the table: DelMe(ID) and there are 30 tables with fk references to its ID that I need to delete first, is there some tool/script that I can run that will generate the 30 delete statements based on the FK relations for me ?
(btw I know about cascade delete on the relations, I can't use it in this existing db)
I'm using Microsoft SQL Server 2008

Answer 1

Here is a script for cascading delete by Aasim Abdullah, works for me on MS SQL Server 2008:
IF OBJECT_ID('dbo.udfGetFullQualName') IS NOT NULL
DROP FUNCTION dbo.udfGetFullQualName;
GO
CREATE FUNCTION dbo.udfGetFullQualName
(#ObjectId INT)
RETURNS VARCHAR (300)
AS
BEGIN
DECLARE #schema_id AS BIGINT;
SELECT #schema_id = schema_id
FROM sys.tables
WHERE object_id = #ObjectId;
RETURN '[' + SCHEMA_NAME(#schema_id) + '].[' + OBJECT_NAME(#ObjectId) + ']';
END
GO
--============ Supporting Function dbo.udfGetOnJoinClause
IF OBJECT_ID('dbo.udfGetOnJoinClause') IS NOT NULL
DROP FUNCTION dbo.udfGetOnJoinClause;
GO
CREATE FUNCTION dbo.udfGetOnJoinClause
(#fkNameId INT)
RETURNS VARCHAR (1000)
AS
BEGIN
DECLARE #OnClauseTemplate AS VARCHAR (1000);
SET #OnClauseTemplate = '[<#pTable>].[<#pCol>] = [<#cTable>].[<#cCol>] AND ';
DECLARE #str AS VARCHAR (1000);
SET #str = '';
SELECT #str = #str + REPLACE(REPLACE(REPLACE(REPLACE(#OnClauseTemplate, '<#pTable>', OBJECT_NAME(rkeyid)), '<#pCol>', COL_NAME(rkeyid, rkey)), '<#cTable>', OBJECT_NAME(fkeyid)), '<#cCol>', COL_NAME(fkeyid, fkey))
FROM dbo.sysforeignkeys AS fk
WHERE fk.constid = #fkNameId; --OBJECT_ID('FK_ProductArrearsMe_ProductArrears')
RETURN LEFT(#str, LEN(#str) - LEN(' AND '));
END
GO
--=========== CASECADE DELETE STORED PROCEDURE dbo.uspCascadeDelete
IF OBJECT_ID('dbo.uspCascadeDelete') IS NOT NULL
DROP PROCEDURE dbo.uspCascadeDelete;
GO
CREATE PROCEDURE dbo.uspCascadeDelete
#ParentTableId VARCHAR (300), #WhereClause VARCHAR (2000), #ExecuteDelete CHAR (1)='N', --'N' IF YOU NEED DELETE SCRIPT
#FromClause VARCHAR (8000)='', #Level INT=0 -- TABLE NAME OR OBJECT (TABLE) ID (Production.Location) WHERE CLAUSE (Location.LocationID = 7) 'Y' IF WANT TO DELETE DIRECTLY FROM SP, IF LEVEL 0, THEN KEEP DEFAULT
AS -- writen by Daniel Crowther 16 Dec 2004 - handles composite primary keys
SET NOCOUNT ON;
/* Set up debug */
DECLARE #DebugMsg AS VARCHAR (4000),
#DebugIndent AS VARCHAR (50);
SET #DebugIndent = REPLICATE('---', ##NESTLEVEL) + '> ';
IF ISNUMERIC(#ParentTableId) = 0
BEGIN -- assume owner is dbo and calculate id
IF CHARINDEX('.', #ParentTableId) = 0
SET #ParentTableId = OBJECT_ID('[dbo].[' + #ParentTableId + ']');
ELSE
SET #ParentTableId = OBJECT_ID(#ParentTableId);
END
IF #Level = 0
BEGIN
PRINT #DebugIndent + ' **************************************************************************';
PRINT #DebugIndent + ' *** Cascade delete ALL data from ' + dbo.udfGetFullQualName(#ParentTableId);
IF #ExecuteDelete = 'Y'
PRINT #DebugIndent + ' *** #ExecuteDelete = Y *** deleting data...';
ELSE
PRINT #DebugIndent + ' *** Cut and paste output into another window and execute ***';
END
DECLARE #CRLF AS CHAR (2);
SET #CRLF = CHAR(13) + CHAR(10);
DECLARE #strSQL AS VARCHAR (4000);
IF #Level = 0
SET #strSQL = 'SET NOCOUNT ON' + #CRLF;
ELSE
SET #strSQL = '';
SET #strSQL = #strSQL + 'PRINT ''' + #DebugIndent + dbo.udfGetFullQualName(#ParentTableId) + ' Level=' + CAST (##NESTLEVEL AS VARCHAR) + '''';
IF #ExecuteDelete = 'Y'
EXECUTE (#strSQL);
ELSE
PRINT #strSQL;
DECLARE curs_children CURSOR LOCAL FORWARD_ONLY
FOR SELECT DISTINCT constid AS fkNameId, -- constraint name
fkeyid AS cTableId
FROM dbo.sysforeignkeys AS fk
WHERE fk.rkeyid <> fk.fkeyid -- WE DO NOT HANDLE self referencing tables!!!
AND fk.rkeyid = #ParentTableId;
OPEN curs_children;
DECLARE #fkNameId AS INT,
#cTableId AS INT,
#cColId AS INT,
#pTableId AS INT,
#pColId AS INT;
FETCH NEXT FROM curs_children INTO #fkNameId, #cTableId; --, #cColId, #pTableId, #pColId
DECLARE #strFromClause AS VARCHAR (1000);
DECLARE #nLevel AS INT;
IF #Level = 0
BEGIN
SET #FromClause = 'FROM ' + dbo.udfGetFullQualName(#ParentTableId);
END
WHILE ##FETCH_STATUS = 0
BEGIN
SELECT #strFromClause = #FromClause + #CRLF + ' INNER JOIN ' + dbo.udfGetFullQualName(#cTableId) + #CRLF + ' ON ' + dbo.udfGetOnJoinClause(#fkNameId);
SET #nLevel = #Level + 1;
EXECUTE dbo.uspCascadeDelete #ParentTableId = #cTableId, #WhereClause = #WhereClause, #ExecuteDelete = #ExecuteDelete, #FromClause = #strFromClause, #Level = #nLevel;
SET #strSQL = 'DELETE FROM ' + dbo.udfGetFullQualName(#cTableId) + #CRLF + #strFromClause + #CRLF + 'WHERE ' + #WhereClause + #CRLF;
SET #strSQL = #strSQL + 'PRINT ''---' + #DebugIndent + 'DELETE FROM ' + dbo.udfGetFullQualName(#cTableId) + ' Rows Deleted: '' + CAST(##ROWCOUNT AS VARCHAR)' + #CRLF + #CRLF;
IF #ExecuteDelete = 'Y'
EXECUTE (#strSQL);
ELSE
PRINT #strSQL;
FETCH NEXT FROM curs_children INTO #fkNameId, #cTableId;
--, #cColId, #pTableId, #pColId
END
IF #Level = 0
BEGIN
SET #strSQL = #CRLF + 'PRINT ''' + #DebugIndent + dbo.udfGetFullQualName(#ParentTableId) + ' Level=' + CAST (##NESTLEVEL AS VARCHAR) + ' TOP LEVEL PARENT TABLE''' + #CRLF;
SET #strSQL = #strSQL + 'DELETE FROM ' + dbo.udfGetFullQualName(#ParentTableId) + ' WHERE ' + #WhereClause + #CRLF;
SET #strSQL = #strSQL + 'PRINT ''' + #DebugIndent + 'DELETE FROM ' + dbo.udfGetFullQualName(#ParentTableId) + ' Rows Deleted: '' + CAST(##ROWCOUNT AS VARCHAR)' + #CRLF;
IF #ExecuteDelete = 'Y'
EXECUTE (#strSQL);
ELSE
PRINT #strSQL;
END
CLOSE curs_children;
DEALLOCATE curs_children;
Usage example 1
Note the use of the fully qualified column name in the example. It's subtle but you must specify the table name for the generated SQL to execute properly.
EXEC uspCascadeDelete
#ParentTableId = 'Production.Location',
#WhereClause = 'Location.LocationID = 2'
Usage example 2
EXEC uspCascadeDelete
#ParentTableId = 'dbo.brand',
#WhereClause = 'brand.brand_name <> ''Apple'''
Usage example 3
exec uspCascadeDelete
#ParentTableId = 'dbo.product_type',
#WhereClause = 'product_type.product_type_id NOT IN
(SELECT bpt.product_type_id FROM dbo.brand_product_type bpt)'

Answer 2

DELETE statements generated for use in SP with parameter, and as ON DELETE triggers:
(this variant supports single column FKs only)
SELECT 'DELETE '+detail.name+' WHERE '+dcolumn.name+' = #'+mcolumn.name AS stmt,
'DELETE ' + detail.name + ' FROM ' + detail.name + ' INNER JOIN deleted ON ' +
detail.name + '.' + dcolumn.name + ' = deleted.' + mcolumn.name AS trg
FROM sys.columns AS mcolumn
INNER JOIN sys.foreign_key_columns ON mcolumn.object_id =
sys.foreign_key_columns.referenced_object_id
AND mcolumn.column_id = sys.foreign_key_columns.referenced_column_id
INNER JOIN sys.tables AS master ON mcolumn.object_id = master.object_id
INNER JOIN sys.columns AS dcolumn
ON sys.foreign_key_columns.parent_object_id = dcolumn.object_id
AND sys.foreign_key_columns.parent_column_id = dcolumn.column_id
INNER JOIN sys.tables AS detail ON dcolumn.object_id = detail.object_id
WHERE (master.name = N'MyTableName')

Answer 3

I'm pretty sure I posted code here on Stack Overflow which does this automatically using INFORMATION_SCHEMA to generate dynamic SQL, but I can't find it. Let me see if I can regenerate it.
You might need to check this out a bit, I couldn't find my original code, so I modified some code I had which builds flattend views for star-schemas automatically.
DECLARE #COLUMN_NAME AS sysname
DECLARE #TABLE_NAME AS sysname
DECLARE #IDValue AS int
SET #COLUMN_NAME = '<Your COLUMN_NAME here>'
SET #TABLE_NAME = '<Your TABLE_NAME here>'
SET #IDValue = 123456789
DECLARE #sql AS varchar(max) ;
WITH RELATED_COLUMNS
AS (
SELECT QUOTENAME(c.TABLE_SCHEMA) + '.'
+ QUOTENAME(c.TABLE_NAME) AS [OBJECT_NAME]
,c.COLUMN_NAME
FROM INFORMATION_SCHEMA.COLUMNS AS c WITH (NOLOCK)
INNER JOIN INFORMATION_SCHEMA.TABLES AS t WITH (NOLOCK)
ON c.TABLE_CATALOG = t.TABLE_CATALOG
AND c.TABLE_SCHEMA = t.TABLE_SCHEMA
AND c.TABLE_NAME = t.TABLE_NAME
AND t.TABLE_TYPE = 'BASE TABLE'
INNER JOIN (
SELECT rc.CONSTRAINT_CATALOG
,rc.CONSTRAINT_SCHEMA
,lkc.TABLE_NAME
,lkc.COLUMN_NAME
FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS rc
WITH (NOLOCK)
INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE lkc
WITH (NOLOCK)
ON lkc.CONSTRAINT_CATALOG = rc.CONSTRAINT_CATALOG
AND lkc.CONSTRAINT_SCHEMA = rc.CONSTRAINT_SCHEMA
AND lkc.CONSTRAINT_NAME = rc.CONSTRAINT_NAME
INNER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS tc
WITH (NOLOCK)
ON rc.CONSTRAINT_CATALOG = tc.CONSTRAINT_CATALOG
AND rc.CONSTRAINT_SCHEMA = tc.CONSTRAINT_SCHEMA
AND rc.UNIQUE_CONSTRAINT_NAME = tc.CONSTRAINT_NAME
INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE rkc
WITH (NOLOCK)
ON rkc.CONSTRAINT_CATALOG = tc.CONSTRAINT_CATALOG
AND rkc.CONSTRAINT_SCHEMA = tc.CONSTRAINT_SCHEMA
AND rkc.CONSTRAINT_NAME = tc.CONSTRAINT_NAME
WHERE rkc.COLUMN_NAME = #COLUMN_NAME
AND rkc.TABLE_NAME = #TABLE_NAME
) AS j
ON j.CONSTRAINT_CATALOG = c.TABLE_CATALOG
AND j.CONSTRAINT_SCHEMA = c.TABLE_SCHEMA
AND j.TABLE_NAME = c.TABLE_NAME
AND j.COLUMN_NAME = c.COLUMN_NAME
)
SELECT #sql = COALESCE(#sql, '') + 'DELETE FROM ' + [OBJECT_NAME]
+ ' WHERE ' + [COLUMN_NAME] + ' = ' + CONVERT(varchar, #IDValue)
+ CHAR(13) + CHAR(10)
FROM RELATED_COLUMNS
PRINT #sql

Answer 4

Another technique is to use a code generator to create the Sql. I'm pretty sure the MyGeneration (no connection) has existing templates to do this. Using that tool and the right template you can create a sql script that deletes the relevant stuff with no pain.

Answer 5

Unfortunately, I think cascading is the tool you're asking for. I understand not being able to use it, but that fact that it exists as a built-in part of the db has pretty much killed the need for an alternative.

Answer 6

You can create all fk columns with a same name like 'row_id'
Then write the code below:
create procedure dbo.deleteRow
#row_id int
as
begin
set nocount on
begin transaction delete_row
declare #mainTableName varchar(50) = 'MyMainTableName'
begin try
declare #OBJECT_ID_mainTable int
select #OBJECT_ID_mainTable = OBJECT_ID from sys.tables where name = #mainTableName
create table #ids ( object_id int , table_name varchar (50) , referenced_object_id int , r_index int )
--1) select all tables are has fk to main table
insert into #ids select t.object id , t.name , fk.referenced object id ,
row_number () over ( order by
--how many tables are depends on me
(select COUNT ( * ) from sys . foreign_key_columns a fk where a_fk.referenced_object_id = fk.parent_object_id ) desc ) r_index
from sys.foreign_key_columns fk
join sys.tables t on t.object_id- fk.parent_object_id
where fk.referenced_object_id = #OBJECT_ID_mainTable
declare #i int = ( select max ( r_index ) from #ids )
declare #sqlBuilder nvarchar ( max )
--2) delete from fk tables in dependet order
while #i > 0
begin
--all fk column are called 'row_id'
set #sqlBuilder = concat ('delete from dbo.[' + ( select table_name from #ids where r_index = #i ) + ']' +
'where row_id = ', #row_id )
exec(#sqlBuilder)
set #i=#i-1
end
--3) delete from main table
delete from <MyMainTableName> where id = #row_id
commit transaction delete_row
end try
begin catch
rollback transaction delete_row
throw
end catch
end