SQL error msg - The DELETE statement conflicted with the SAME TABLE REFERENCE constraint

Question

Executed as user: ****. The DELETE statement
conflicted with the SAME TABLE REFERENCE constraint "FK_PARENT_TASK_REF".
The conflict occurred in database "****", table "****", column
'PARENT_TASK_ID'. [SQLSTATE 23000] (Error 547) The statement has been
terminated. [SQLSTATE 01000] (Error 3621). The step failed.
Does this error msg indicate the whole script failed to execute or was it just a single step/task that failed ?
What does error msg mean ?
Anyway to prevent this error msg and ensure script runs successfully

Answer 1

Hi mdavidh,
This error occurs because the record  'PARENT_TASK_ID' was referenced by 'FK_PARENT_TASK_REF'.
Please refer below codes:
CREATE TABLE MyTable (
ID INT, primary key(ID), -- primary key
ID_Parent INT foreign key(ID_Parent) references MyTable(ID), -- foreign key reference the same table
insert into MyTable(ID,ID_Parent)
values(0,0);
insert into MyTable(ID,ID_Parent)
values(1,0);
insert into MyTable(ID,ID_Parent)
values(2,0);
insert into MyTable(ID,ID_Parent)
values(3,1);
insert into MyTable(ID,ID_Parent)
values(4,3);
insert into MyTable(ID,ID_Parent)
values(5,4);
CREATE TRIGGER MyTrigger
on MyTable
instead of delete
as
set nocount on
update MyTable set ID_Parent = null where ID_Parent in (select ID from deleted)
delete from MyTable where ID in (select ID from deleted)
Now we could delete records.
delete from MyTable where ID_Parent=0
Thanks,
Candy Zhou