1992
MariaDBWARNINGCriticalSchemaHIGH confidence
Converting column to a different type
Production Risk
Low — schema may differ from intention; existing data is unaffected.
What this means
MySQL automatically converted a column definition to a different but compatible type during a CREATE TABLE or ALTER TABLE. For example, a CHAR column too wide may be silently promoted to TEXT.
Why it happens
- 1Column length exceeds the maximum for the requested type.
- 2Implicit type promotion rules triggered by the storage engine or character set.
- 3Creating a column with a type that the storage engine normalises.
How to reproduce
trigger — this will error
trigger — this will error
CREATE TABLE t (col CHAR(300));
expected output
Warning 1292: Incorrect datetime value. (similar auto-convert warning for other types)
Fix 1
Use the intended type explicitly to avoid silent promotion
Use the intended type explicitly to avoid silent promotion
CREATE TABLE t (col TEXT); -- if large text is needed
Why this works
Explicit typing prevents unexpected schema changes.
Fix 2
Review SHOW WARNINGS after DDL
Review SHOW WARNINGS after DDL
SHOW WARNINGS;
Why this works
Auto-convert warnings are surfaced here.
What not to do
✕
Sources
Official documentation ↗
MySQL 8.0 — 1992 ER_AUTO_CONVERT
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