EC
1761
MySQLERRORNotableForeign KeysHIGH confidence

Foreign key constraint violation — duplicate key with child info

Production Risk

Medium — operation rejected; referential integrity maintained.

What this means

A foreign key violation was detected and the error message includes information about the child table that references the conflicting key.

Why it happens
  1. 1Attempting to delete or update a parent row that is still referenced by child rows.
  2. 2Attempting to insert a child row with a key value that does not exist in the parent.
How to reproduce
trigger — this will error
trigger — this will error
DELETE FROM customers WHERE id = 1; -- orders references customer 1

expected output

ERROR 1761 (23000): Foreign key constraint fails (`db`.`orders`, CONSTRAINT `fk_cust` FOREIGN KEY (`customer_id`) REFERENCES `customers` (`id`)).

Fix

Delete or update child rows before modifying the parent

Delete or update child rows before modifying the parent
DELETE FROM orders WHERE customer_id = 1;
DELETE FROM customers WHERE id = 1;

Why this works

Removes referencing rows first so the parent row can be modified safely.

What not to do

✕

Sources
Official documentation ↗

MySQL 8.0 — 1761 ER_FOREIGN_DUPLICATE_KEY_WITH_CHILD_INFO

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