Is Using Multiple SELECT Statements Efficient for Upserting with Complex Tables?

Upserting with Complex Tables: Updating Multiple Columns

When performing upsert operations with multiple columns, the question arises of whether it's efficient to use multiple select statements in the update part. While it's technically feasible, a better approach is available.

Consider the example provided:

INSERT INTO `item`
(`item_name`, items_in_stock)
VALUES('A', 27)
ON DUPLICATE KEY UPDATE
`new_items_count` = 27 + (SELECT items_in_stock where item_name = 'A')

This query effectively adds the incoming quantity to the existing value for the specified item. However, the subselect is unnecessary.

The corrected version of the query is as follows:

INSERT INTO `item`
(`item_name`, items_in_stock)
VALUES( 'A', 27)
ON DUPLICATE KEY UPDATE
`new_items_count` = `new_items_count` + 27

By omitting the subselect, the query utilizes MySQL's ability to reference the row that triggered the ON DUPLICATE KEY action. This eliminates the need for additional select statements and streamlines the update process.

Remember that simplicity is often the key to efficient operations. By carefully considering the available options and avoiding unnecessary complexity, you can optimize your upsert queries for performance and code readability.

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