Cannot delete or update a parent row: a foreign key constraint fails

Question

The simple way would be to disable the foreign key check; make the changes then re-enable foreign key check.

SET FOREIGN_KEY_CHECKS=0; -- to disable them
SET FOREIGN_KEY_CHECKS=1; -- to re-enable them

As is, you must delete the row out of the advertisers table before you can delete the row in the jobs table that it references. This:

ALTER TABLE `advertisers`
  ADD CONSTRAINT `advertisers_ibfk_1` FOREIGN KEY (`advertiser_id`) 
      REFERENCES `jobs` (`advertiser_id`);

...is actually the opposite to what it should be. As it is, it means that you'd have to have a record in the jobs table before the advertisers. So you need to use:

ALTER TABLE `jobs`
  ADD CONSTRAINT `advertisers_ibfk_1` FOREIGN KEY (`advertiser_id`) 
      REFERENCES `advertisers` (`advertiser_id`);

Once you correct the foreign key relationship, your delete statement will work.

Under your current (possibly flawed) design, you must delete the row out of the advertisers table before you can delete the row in the jobs table that it references.

Alternatively, you could set up your foreign key such that a delete in the parent table causes rows in child tables to be deleted automatically. This is called a cascading delete. It looks something like this:

ALTER TABLE `advertisers`
ADD CONSTRAINT `advertisers_ibfk_1`
FOREIGN KEY (`advertiser_id`) REFERENCES `jobs` (`advertiser_id`)
ON DELETE CASCADE;

Having said that, as others have already pointed out, your foreign key feels like it should go the other way around since the advertisers table really contains the primary key and the jobs table contains the foreign key. I would rewrite it like this:

ALTER TABLE `jobs`
ADD FOREIGN KEY (`advertiser_id`) REFERENCES `advertisers` (`advertiser_id`);

And the cascading delete won't be necessary.

Disable the foreign key check and make the changes then re-enable foreign key check.

SET FOREIGN_KEY_CHECKS=0; -- to disable them
DELETE FROM `jobs` WHERE `job_id` = 1 LIMIT 1 
SET FOREIGN_KEY_CHECKS=1; -- to re-enable them

If you want to drop a table you should execute the following query in a single step

SET FOREIGN_KEY_CHECKS=0; DROP TABLE table_name;

I tried the solution mentioned by @Alino Manzi but it didn't work for me on the WordPress related tables using wpdb.

then I modified the code as below and it worked

SET FOREIGN_KEY_CHECKS=OFF; //disabling foreign key

//run the queries which are giving foreign key errors

SET FOREIGN_KEY_CHECKS=ON; // enabling foreign key

I think that your foreign key is backwards. Try:

ALTER TABLE 'jobs'
ADD CONSTRAINT `advertisers_ibfk_1` FOREIGN KEY (`advertiser_id`) REFERENCES `advertisers` (`advertiser_id`)