How to Insert Rows Without Errors in MySQL When a Unique Key Already Exists?

INSERT ... ON DUPLICATE KEY: A Null Operation

Question:

In a table with a unique key for two columns, how can you insert a row without triggering an error if the key already exists?

Answer:

MySQL offers several options for handling duplicate key conflicts during insertions.

INSERT ... ON DUPLICATE KEY UPDATE>

A simple but effective method is to use INSERT ... ON DUPLICATE KEY UPDATE>. This syntax instructs MySQL to update the id column to its existing value if a duplicate key is encountered. However, this won't actually trigger an update, since id is being set to its current value.

INSERT IGNORE

If you're not concerned about errors or autoincrement field exhaustion, INSERT IGNORE is a straightforward option. This syntax simply ignores any errors that would result from duplicate key conflicts, including conversion errors, foreign key errors, and autoincrement field exhaustion.

Benefits:

• Prevents duplicate key errors
• Maintains data integrity with INSERT ... ON DUPLICATE KEY UPDATE>
• Avoids unintended insertions with INSERT IGNORE

Considerations:

• INSERT IGNORE can lead to data loss if a row with data other than the unique key fields should be inserted.
• INSERT ... ON DUPLICATE KEY UPDATE> may not be suitable if you need to perform additional updates on duplicate rows.

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