3133
MariaDBERRORNotableConstraintsHIGH confidence
Duplicate value in index but value is unknown
Production Risk
Medium — duplicate key errors indicate data integrity issues.
What this means
A unique index violation was detected but the duplicate value cannot be shown, typically because the column uses a type or collation that obscures the duplicate in the error message.
Why it happens
- 1Inserting or updating a row that would create a duplicate in a unique or primary key index.
- 2The value cannot be displayed (e.g., binary or encrypted column).
How to reproduce
trigger — this will error
trigger — this will error
INSERT INTO t1 (id) VALUES (1), (1);
expected output
ERROR 3133 (23000): Duplicate entry for key 'PRIMARY'.
Fix 1
Identify and remove duplicate rows before inserting
Identify and remove duplicate rows before inserting
SELECT col, COUNT(*) FROM t1 GROUP BY col HAVING COUNT(*) > 1;
Why this works
Locates existing duplicates so they can be resolved.
Fix 2
Use INSERT IGNORE or ON DUPLICATE KEY UPDATE
Use INSERT IGNORE or ON DUPLICATE KEY UPDATE
INSERT IGNORE INTO t1 (id) VALUES (1);
Why this works
Silently skips the duplicate row insertion.
What not to do
✕
Sources
Official documentation ↗
MySQL 8.0 — 3133 ER_DUP_UNKNOWN_IN_INDEX2
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