Mysql error 1452 - Cannot add or update a child row: a foreign key constraint fails

Question

I\'m having a bit of a strange problem. I\'m trying to add a foreign key to one table that references another, but it is failing for some reason. With my limited knowledge o

Answer 1

you can try this exapmple

 START TRANSACTION;
 SET foreign_key_checks = 0;
 ALTER TABLE `job_definers` ADD CONSTRAINT `job_cities_foreign` FOREIGN KEY 
 (`job_cities`) REFERENCES `drop_down_lists`(`id`) ON DELETE CASCADE ON UPDATE CASCADE;
 SET foreign_key_checks = 1;
 COMMIT;

Note : if you are using phpmyadmin just uncheck Enable foreign key checks

as example

hope this soloution fix your problem :)