MySQL 1218: Cannot delete child row.

What is MySQL 1218: Cannot delete child row.

When encountering the error "1218: Cannot delete child row" in MySQL, it typically indicates a foreign key constraint violation, meaning you're trying to delete a record from a parent table that has dependent records in a child table. Here are actionable steps:

Identify the Foreign Key Constraint and Related Tables:

- Run the following query to find the foreign key constraint that is causing the issue. Replace `yourtablename` with the name of the table you're trying to delete from.SELECT CONSTRAINTNAME, TABLENAME, COLUMNNAME, REFERENCEDTABLENAME, REFERENCEDCOLUMN_NAME FROM INFORMATIONSCHEMA.KEYCOLUMN_USAGE WHERE TABLESCHEMA = 'yourdatabasename' AND TABLENAME = 'yourtablename';

Check Dependent Rows in the Child Table:

- Use the information from step 1 to identify the child table and its related column. Then, check for dependent rows that are preventing the delete operation. For example, if your foreign key is in `childtable` and references a column in `parenttable`, you would run:SELECT * FROM childtable WHERE foreignkeycolumn = 'valuethatyoutriedtodelete';

Decide on the Action for Dependent Rows:

- Based on your application's requirements, you may either: - Delete the dependent rows: Execute a delete statement on the child table to remove the dependent rows. For example:DELETE FROM childtable WHERE foreignkeycolumn = 'valuethatyoutriedtodelete'; - Update the dependent rows: If deleting is not an option, you may need to update the foreign key column in the child table to point to a different parent record or set it to `NULL` if the foreign key constraint allows it. Example:UPDATE childtable SET foreignkeycolumn = 'newvalueorNULL' WHERE foreignkeycolumn = 'valuethatyoutriedto_delete';

Retry the Delete Operation:

- After resolving the dependent rows issue, try to execute your delete operation again on the parent table.Remember to replace `yourdatabasename`, `yourtablename`, `childtable`, `foreignkeycolumn`, `valuethatyoutriedtodelete`, and `newvalueor_NULL` with the actual values applicable to your scenario.