MySQL Error 1062: Duplicate Entry for Key (Fix Guide)

The Error Message

What Causes MySQL 1062?

MySQL Error 1062 fires when you try to INSERT or UPDATE a row with a value that already exists in a column with a UNIQUE or PRIMARY KEY constraint.

Common Causes

How to Fix It

Step 1: Use INSERT IGNORE to skip duplicates

INSERT IGNORE skips the row if a duplicate key violation occurs, without throwing an error.

-- Silently skip rows that would cause duplicates:
INSERT IGNORE INTO users (email, name)
VALUES ('john@example.com', 'John');

Step 2: Use ON DUPLICATE KEY UPDATE

This is the best approach for upserts — insert if new, update if exists.

-- Update the existing row instead:
INSERT INTO users (email, name, updated_at)
VALUES ('john@example.com', 'John Updated', NOW())
ON DUPLICATE KEY UPDATE
  name = VALUES(name),
  updated_at = VALUES(updated_at);

Step 3: Check for existing data first

Query first to see if the data already exists, then decide whether to insert or update.

-- Check before inserting:
SELECT id, email FROM users
WHERE email = 'john@example.com';

-- Or use NOT EXISTS:
INSERT INTO users (email, name)
SELECT 'john@example.com', 'John'
FROM DUAL
WHERE NOT EXISTS (
  SELECT 1 FROM users WHERE email = 'john@example.com'
);

Step 4: Fix auto-increment counter

If auto-increment is out of sync, resetting it prevents future collisions.

-- Reset auto-increment to max existing ID + 1:
ALTER TABLE users AUTO_INCREMENT = 1;

-- Or set it to a specific value:
SELECT MAX(id) FROM users;
ALTER TABLE users AUTO_INCREMENT = 1001;

How to Prevent This Error

Design your schema with proper unique constraints from the start. Use upsert patterns (ON DUPLICATE KEY UPDATE) when importing data. Always use auto-increment for primary keys unless you have a specific reason not to.

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Frequently Asked Questions