Disabling foreign key checks in MySQL is usefull when you are dealing with tables that use foreign keys (InnoDB engine).
You can not delete (drop) multiple tables, a parent table or a child table until you disable foreign key checks four your current database.
The sql command to disable foreign key checks is:
SET FOREIGN_KEY_CHECKS = 0;
To enable the foreign key checks use the opposite command:
SET FOREIGN_KEY_CHECKS = 1;