INSERT vs. UPDATE on Duplicate Keys: How to Handle Conflicts in MySQL?

On Duplicate Key Handling

When inserting unique values into a database table, it's common to encounter the scenario where duplicate records are detected. In such cases, you have options to determine how to handle these conflicts.

INSERT IGNORE vs. INSERT ON DUPLICATE KEY UPDATE

The INSERT IGNORE statement simply ignores all errors and continues inserting rows. However, it's not recommended as it can lead to unforeseen consequences and data inconsistency.

Instead, a more suitable option is INSERT ON DUPLICATE KEY UPDATE, which allows you to specify an update action when a conflict occurs. In your case, where the unique key is the tag field, you can use the following syntax:

INSERT INTO table_tags (tag) VALUES ('tag_a'),('tab_b'),('tag_c')
ON DUPLICATE KEY UPDATE tag=tag;

This statement attempts to insert the specified values. If any of the tags already exist, the update clause will simply set the tag value to itself, effectively ignoring the duplicate tag.

Testing the Query

Executing the query will result in the following output:

Query OK, 0 rows affected (0.07 sec)

This confirms that the duplicate tags were ignored, and the remaining rows were successfully inserted.

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