Why Do I Get "ERROR 1217 (23000)... foreign key constraint fails" When Dropping Tables in MySQL?

MySQL: Handling Bogus Foreign Key Constraint Fails

Encountering the "ERROR 1217 (23000)... foreign key constraint fails" error while attempting to drop a MySQL table, despite having seemingly removed all corresponding foreign key constraints, can be puzzling.

To resolve this issue, consider the following possibility:

Data Persistence Due to Multiple Connections

When using database management tools like MySQL Query Browser or phpMyAdmin, it's observed that a new connection is established for each query. This means that when tables are dropped individually, the database may still hold foreign key references that are orphaned and not accounted for in the current connection.

Solution: Consolidated Drop Statements

To remedy this situation, consolidate all drop statements into a single query. For example:

SET FOREIGN_KEY_CHECKS=0;
DROP TABLE my_first_table_to_drop;
DROP TABLE my_second_table_to_drop;
SET FOREIGN_KEY_CHECKS=1;

By grouping all drop statements together, foreign key constraints are disabled while the tables are dropped. The additional statement SET FOREIGN_KEY_CHECKS=1 serves as an added precaution to re-enable foreign key checks after the operation is complete.

The above is the detailed content of Why Do I Get "ERROR 1217 (23000)... foreign key constraint fails" When Dropping Tables in MySQL?. For more information, please follow other related articles on the PHP Chinese website!