Phenomenon

MySQL appears when deleting a table

ERROR 1217 (23000): Cannot delete or update a parent row: a foreign key constraint fails

Why

It may be that in mysql, the foreign key association is set between the deleted table and another table, which makes it impossible to update or delete data

Solutions

By setting foreign_ KEY_ Checks variable to avoid this

Disable foreign key constraints

SET FOREIGN_KEY_CHECKS = 0;

Then you can delete the table

Start the foreign key constraint after deletion

SET FOREIGN_KEY_CHECKS = 1;

View current foreign_ KEY_ The value of checks can be determined by the following command

SELECT  @@FOREIGN_KEY_CHECKS;

Attention

This setting will only affect the current session, not the global

If you want to set global variables, you can write like this

SET GLOBAL FOREIGN_KEY_CHECKS = 0;