How to Simulate an Upsert in Microsoft Access Using UPDATE and LEFT JOIN?

Insert or Update (Upsert) in Microsoft Access

Question:

In Microsoft Access 2000, you want to perform an operation that updates a row if it exists and inserts a new row if it does not exist.

Solution:

Use UPDATE and LEFT JOIN to simulate Upsert

You can simulate an upsert in Access using an UPDATE query with a LEFT JOIN. The query uses LEFT JOIN to check if there is an existing row and then updates or inserts accordingly:

UPDATE b
LEFT JOIN a ON b.id = a.id
SET a.f1 = b.f1,
    a.f2 = b.f2,
    a.f3 = b.f3;

In this query, "b" represents new data and "a" represents an existing table. If there is a matching row in "a", the query updates the value in "a" with the corresponding value in "b". Otherwise, the query inserts a new row into "a" using the value from "b".

Simplified example:

For clarity, here is a simplified version of the query:

UPDATE main_table RIGHT JOIN new_data 
    ON main_table.id = new_data.id
SET
    main_table.id = new_data.id,
    main_table.col_1 = new_data.col_1,
    main_table.col_2 = new_data.col_2;

This query will update or insert rows in "main_table" based on the values ​​in "new_data". The "id" column is the matching condition, and the values ​​being updated or inserted are "col_1" and "col_2".

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