Question

I have a stored procedure that starts a transactions. Inside it, I disable some of the constraints. I modify the data. And then enable the constraints.
What I want is to rollback if the data in inconsistent in the end of the SP (prior to calling commit of course).

Currently I run DBCC CHECKCONSTRAINTS in the end to see what was broken.
But can I just rollback when DBCC CHECKCONSTRAINTS outputs any data?

Or better: Can the DBCC CHECKCONSTRAINTS raise error if any of the constraints are broken?

Answer 1

Instead of using DBCC CHECKCONSTRAINTS, when you enable the constraints again, use the WITH CHECK option.

ALTER TABLE YourTable WITH CHECK CHECK CONSTRAINT YourConstraint;

If there is a violation, you’ll get an error like:

Msg 547, Level 16, State 0, Line 15
The ALTER TABLE statement conflicted with the FOREIGN KEY constraint "YourConstraint". The conflict occurred in database "YourDatabase", table "YourTable", column 'YourColumn'.

Use the sample code below for a simple demonstration.

use tempdb
go

create table a (
    id int primary key
)

create table b (
    id int
) 

alter table b add constraint x foreign key (id) references a(id)

alter table b nocheck constraint x

insert into b (id) values (1)

alter table b with check check constraint x
go

drop table b
drop table a
go