I'm trying to create a constraint with both on update and delete in tsql. I've tried a couple of different methods, and now I'm a little stuck & frustrated - seems so simple. I know you can't alter an existing constraint so I'm not sure about how to do this;
alter table AllowedCars
add constraint FK_AllowedCars_CarID foreign key (CarID)
references Cars(LocusID) on delete cascade,
constraint FK_AllowedCars_CarID foreign key (CarID)
references Cars(CarID) on update cascade
or this;
alter table AllowedCars add constraint FK_AllowedCars_CarID foreign key (CarID)
references Cars(CarID) on delete cascade and on update cascade
You need to drop constraint first, and then recreate it. Your second attempt was right, but you needed to remove and.
alter table AllowedCars
drop constraint FK_AllowedCars_CarID
alter table AllowedCars
add constraint FK_AllowedCars_CarID
foreign key (CarID)
references Cars(CarID)
on delete cascade
on update cascade
Related
ALTER TABLE ONLY rental ADD CONSTRAINT rental_customer_id_fkey FOREIGN KEY (customer_id) REFERENCES customer(customer_id) ON UPDATE CASCADE ON DELETE RESTRICT;
ERROR: there is no unique constraint matching given keys for referenced table "customer"
ALTER TABLE ONLY customer ADD CONSTRAINT customer_store_id_fkey FOREIGN KEY (store_id) REFERENCES store(store_id) ON UPDATE CASCADE ON DELETE RESTRICT;
ALTER TABLE ONLY film ADD CONSTRAINT film_language_id_fkey FOREIGN KEY (language_id) REFERENCES language(language_id) ON UPDATE CASCADE ON DELETE RESTRICT;
ALTER TABLE ONLY inventory ADD CONSTRAINT inventory_store_id_fkey FOREIGN KEY (store_id) REFERENCES store(store_id) ON UPDATE CASCADE ON DELETE RESTRICT;
ERROR: insert or update on table "inventory" violates foreign key constraint
I get these messages when i use the query tool for a sql query of over 1300 lines of code. I'm still learning so any pointers will be helpful
ALTER TABLE WORKS_ON ADD constraint
companyFK3 FOREIGN KEY(Essn)
REFERENCES EMPLOYEE (Ssn);
ALTER TABLE WORKS_ON ADD constraint
companyFK4 FOREIGN KEY(Pno)
REFERENCES PROJECT (Pnumber);
The problem is i don't know how to add CASCADE DELETE FOR it
.
Link to DB:https://www.db-fiddle.com/f/xhEj2sAgdTMABBkCtJvmoC/0#&togetherjs=z3CKywAccH
ALTER TABLE WORKS_ON ADD constraint
companyFK3 FOREIGN KEY(Essn)
REFERENCES EMPLOYEE (Ssn) ON DELETE CASCADE;
ALTER TABLE WORKS_ON ADD constraint
companyFK4 FOREIGN KEY(Pno)
REFERENCES PROJECT (Pnumber) ON DELETE CASCADE;
In a previous command, I foolishly wrote:
alter table UserInfo
add column gcal_id integer references GoogleCal on delete cascade
I've since realized that I don't want on delete cascade. How do I alter gcal-id in UserInfo to no longer have that constraint without losing the information saved in current entries?
Happily, it's fairly simple.
First \d+ UserInfo to see the constraint name, which will appear below the table's column definitions.
In your case it will probably be something like
Foreign-key constraints:
"userinfo_gcal_id_fkey" FOREIGN KEY (gcal_id) REFERENCES googlecal(id) ON DELETE CASCADE
Then, just drop and re-add the constraint in one command:
ALTER TABLE UserInfo
DROP CONSTRAINT userinfo_gcal_id_fkey,
ADD CONSTRAINT userinfo_gcal_id_fkey FOREIGN KEY (gcal_id) REFERENCES googlecal(id);
omitting the ON DELETE CASCADE part.
I have a table with a foreign key reference and I had added a on_delete_cascade condition with that foreign key.
I don't need the rows to be deleted even if the foreign key object gets deleted.
How can I change the drop condition without have to drop the column?
Just drop the conatraint and then add it back without the ON DELETE CASCADE clause:
ALTER TABLE some_table DROP CONSTRAINT some_key,
ADD CONSTRAINT some_key FOREIGN KEY (id) REFERENCES tab(a_id);
Check what the real experts wrote by reading here:
https://www.postgresql.org/message-id/CABvLTWHdT0tTygV0-O_ZgLRRAGZAg0W4zvghfF2PshAzvkAaGg%40mail.gmail.com
In order to delete some rows referenced by a foreign key constraint without cascading on delete, I created a temporary foreign key constraint, deleted the row, and then deleted the temporary constraint:
ALTER TABLE rel_user_right
ADD CONSTRAINT temp_fk_rel_user_right_user_right_02
FOREIGN KEY (right_id) REFERENCES user_right (id)
ON DELETE CASCADE;
DELETE FROM user_right WHERE "name" LIKE '%.statusLight.%';
ALTER TABLE rel_user_right
DROP CONSTRAINT temp_fk_rel_user_right_user_right_02;
where this table already had the following constraint defined on it:
ALTER TABLE rel_user_right
ADD CONSTRAINT fk_rel_user_right_user_right_02
FOREIGN KEY (right_id) REFERENCES user_right (id);
This worked fine for me, but seems to have failed on my colleague's computer. As you can see, the two FK constraints define conflicting ON DELETE behaviour. Is precedence defined in this situation, or is it non-deterministic?
Postgres allows to create two references differing only in ON DELETE clause.
I could find no information on the impact of such a case.
In my tests I was unable to cover the existing constraint with new one (i.e. DELETE was always restricted despite of the existence of the second cascading constraint).
However this behaviour is undocumented and one should not rely on it.
The normal way to proceed should be replacing the old constraint with new one:
ALTER TABLE rel_user_right
ADD CONSTRAINT fk_rel_user_right_user_right_temp
FOREIGN KEY (right_id) REFERENCES user_right (id)
ON DELETE CASCADE,
DROP CONSTRAINT fk_rel_user_right_user_right;
DELETE FROM user_right WHERE "name" LIKE '%.statusLight.%';
ALTER TABLE rel_user_right
ADD CONSTRAINT fk_rel_user_right_user_right
FOREIGN KEY (right_id) REFERENCES user_right (id),
DROP CONSTRAINT fk_rel_user_right_user_right_temp;
DISABLE CONSTRAINT would be useful here, but there is no such feature in Postgres (there have been attempts to implement it, but they did not end in success). You can use DISABLE TRIGGER for it, but the above solution is simpler and more natural.