4118
MariaDBERRORNotableHIGH confidence
Foreign key column data type mismatch
Production Risk
Low — DDL fails; no data is modified.
Why it happens
- 1The FK column and the referenced column have different data types (e.g., INT vs BIGINT).
- 2Signed vs unsigned mismatch between FK and referenced integer columns.
Fix
Align the FK column data type with the referenced column
Align the FK column data type with the referenced column
ALTER TABLE child MODIFY fk_col BIGINT UNSIGNED;
Why this works
Matching the referenced column type exactly satisfies the FK type requirement.
What not to do
✕
Sources
Official documentation ↗
MySQL 8.0 — 4118 ER_FK_COLUMN_MISMATCH
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