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ERROR 23505
PostgreSQL Unique Constraint Violation
Database Error
An INSERT or UPDATE attempted to create a duplicate value in a column with a UNIQUE constraint.
Root Cause
Trying to insert a row with a value that already exists in a unique-indexed column (e.g., duplicate email, duplicate username).
How to Fix
Use INSERT ... ON CONFLICT DO NOTHING or ON CONFLICT DO UPDATE to handle duplicates gracefully. Or check for existence before inserting.
Quick Summary
PostgreSQL error 23505: unique constraint violation. Handle with ON CONFLICT DO NOTHING or ON CONFLICT DO UPDATE. Return a 409 Conflict HTTP status to the client.
Key Takeaways
Key Takeaways
- Error code 23505 = unique_violation in PostgreSQL
- Handle with ON CONFLICT: INSERT ... ON CONFLICT (email) DO NOTHING
- Return HTTP 409 Conflict to the client
- The error detail includes the constraint name and duplicate value
Use Cases
When to use it
- Duplicate email registration
- Duplicate username
- Duplicate order ID
Watch out
Common Mistakes
- Returning 500 instead of 409 for unique constraint violations
- Not handling the error gracefully, always catch and return a meaningful error message
FAQ
23505 PostgreSQL Unique Constraint Violation, Frequently Asked
How do I get the duplicate value from the error?
In Node.js with pg: error.detail contains the duplicate key value. Parse it to show a user-friendly message.
Still having issues?
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