How to Handle Duplicate Entry Errors in MySQL: INSERT...IGNORE, REPLACE INTO, or INSERT...ON DUPLICATE KEY UPDATE?

Ignoring Duplicate Entry Errors in MySQL

Database insertions can sometimes result in duplicate entry errors when attempting to add records with unique identifiers. MySQL provides several alternatives to handle such errors.

One option is to use the INSERT...IGNORE syntax, which prevents error generation in the event of a duplicate entry. It simply skips the insertion without any notification.

Another approach is to employ REPLACE INTO, which replaces an existing record with the same key value. Instead of ignoring the insert, it overwrites the old record with the new one.

Finally, INSERT...ON DUPLICATE KEY UPDATE allows for an update operation to be performed on duplicate key encounters. This means that instead of attempting to insert a new record, MySQL will update the existing record with the provided values.

Example:

Consider a table named tbl with columns id and value. Initially, it contains a single entry: id=1 and value=1. Running the following statements demonstrates the behavior of each syntax:

• REPLACE INTO tbl VALUES(1,50);: Updates the existing record, resulting in id=1 and value=50.
• INSERT IGNORE INTO tbl VALUES (1,10);: Inserts nothing, as the duplicate key exists.
• INSERT INTO tbl VALUES (1,200) ON DUPLICATE KEY UPDATE value=200;: Updates the existing record, resulting in id=1 and value=200.

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