EC
4110
MySQLERRORNotableHIGH confidence

Foreign key columns changed via DDL

Production Risk

Medium — DDL fails; the table schema remains unchanged until the FK is handled.

Why it happens
  1. 1An ALTER TABLE tried to change the data type or properties of a column used in an FK.
  2. 2A column rename was attempted on an FK column without dropping the FK first.

Fix

Drop the FK, alter the column, then recreate the FK

Drop the FK, alter the column, then recreate the FK
ALTER TABLE t DROP FOREIGN KEY fk_name; ALTER TABLE t MODIFY col INT; ALTER TABLE t ADD CONSTRAINT fk_name FOREIGN KEY (col) REFERENCES other(id);

Why this works

Removing the FK constraint temporarily allows the column modification to proceed.

What not to do

✕

Sources
Official documentation ↗

MySQL 8.0 — 4110 ER_FOREIGN_KEY_COLUMNS_CHANGED

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