I just need some in help to implement delete cascade in my stored procedure because I have REFERENCE constraint error
Create PROCEDURE [dbo].[DeleteProject]
@ProjectID uniqueidentifier
AS
BEGIN
-- Insert statements for procedure here
DELETE FROM [TaskManagementSystem_DB].[dbo].[Projects]
WHERE projectID = @ProjectID
END
You don't implement delete cascade in the proc.
You either implement delete cascase on the foriegn key constraint itself:
ALTER TABLE [ChildTable] WITH CHECK ADD CONSTRAINT [FK_ChildTable_Projects] FOREIGN KEY ([ProjectID})
REFERENCES [Project] ([ProjectID])
ON DELETE CASCADE
or you need to explicitly delete the child record before you delete the master.
Create PROCEDURE [dbo].[DeleteProject]
@ProjectID uniqueidentifier
AS
BEGIN
DELETE child
FROM [TaskManagementSystem_DB].[dbo].[Projects] proj
JOIN [TaskManagementSystem_DB].[dbo].[ChildTable] child
ON proj.ProjectID = child.ProjectID
DELETE FROM [TaskManagementSystem_DB].[dbo].[Projects]
WHERE projectID = @ProjectID
END
Here you can find a implementation that deletes all rows in the table specified that conform to the criteria selected, while also deleting any child/grandchild records and so on.
It first reads the sysforeignkeys table to find any child tables, then deletes the soon-to-be orphan records from them using recursive calls to this procedure. Once all child records are gone, the rows are deleted from the selected table: Awesome SQL Delete Cascade Stored Procedure!
Here it is the code, in case you are having problems following the link:
CREATE Procedure spDeleteRows
/*
Recursive row delete procedure.
It deletes all rows in the table specified that conform to the criteria selected,
while also deleting any child/grandchild records and so on. This is designed to do the
same sort of thing as Access's cascade delete function. It first reads the sysforeignkeys
table to find any child tables, then deletes the soon-to-be orphan records from them using
recursive calls to this procedure. Once all child records are gone, the rows are deleted
from the selected table. It is designed at this time to be run at the command line. It could
also be used in code, but the printed output will not be available.
*/
(
@cTableName varchar(50), /* name of the table where rows are to be deleted */
@cCriteria nvarchar(1000), /* criteria used to delete the rows required */
@iRowsAffected int OUTPUT /* number of records affected by the delete */
)
As
set nocount on
declare @cTab varchar(255), /* name of the child table */
@cCol varchar(255), /* name of the linking field on the child table */
@cRefTab varchar(255), /* name of the parent table */
@cRefCol varchar(255), /* name of the linking field in the parent table */
@cFKName varchar(255), /* name of the foreign key */
@cSQL nvarchar(1000), /* query string passed to the sp_ExecuteSQL procedure */
@cChildCriteria nvarchar(1000), /* criteria to be used to delete
records from the child table */
@iChildRows int /* number of rows deleted from the child table */
/* declare the cursor containing the foreign key constraint information */
DECLARE cFKey CURSOR LOCAL FOR
SELECT SO1.name AS Tab,
SC1.name AS Col,
SO2.name AS RefTab,
SC2.name AS RefCol,
FO.name AS FKName
FROM dbo.sysforeignkeys FK
INNER JOIN dbo.syscolumns SC1 ON FK.fkeyid = SC1.id
AND FK.fkey = SC1.colid
INNER JOIN dbo.syscolumns SC2 ON FK.rkeyid = SC2.id
AND FK.rkey = SC2.colid
INNER JOIN dbo.sysobjects SO1 ON FK.fkeyid = SO1.id
INNER JOIN dbo.sysobjects SO2 ON FK.rkeyid = SO2.id
INNER JOIN dbo.sysobjects FO ON FK.constid = FO.id
WHERE SO2.Name = @cTableName
OPEN cFKey
FETCH NEXT FROM cFKey INTO @cTab, @cCol, @cRefTab, @cRefCol, @cFKName
WHILE @@FETCH_STATUS = 0
BEGIN
/* build the criteria to delete rows from the child table. As it uses the
criteria passed to this procedure, it gets progressively larger with
recursive calls */
SET @cChildCriteria = @cCol + ' in (SELECT [' + @cRefCol + '] FROM [' +
@cRefTab +'] WHERE ' + @cCriteria + ')'
print 'Deleting records from table ' + @cTab
/* call this procedure to delete the child rows */
EXEC spDeleteRows @cTab, @cChildCriteria, @iChildRows OUTPUT
FETCH NEXT FROM cFKey INTO @cTab, @cCol, @cRefTab, @cRefCol, @cFKName
END
Close cFKey
DeAllocate cFKey
/* finally delete the rows from this table and display the rows affected */
SET @cSQL = 'DELETE FROM [' + @cTableName + '] WHERE ' + @cCriteria
print @cSQL
EXEC sp_ExecuteSQL @cSQL
print 'Deleted ' + CONVERT(varchar, @@ROWCOUNT) + ' records from table ' + @cTableName
