Understanding SQL Anti-Joins: Retain Rows Not Found in Another Table

To perform a LEFT ANTI JOIN in SQL, you can use the following approach:

SELECT *
FROM tableA
LEFT JOIN tableB ON tableA.key = tableB.key
WHERE tableB.key IS NULL;

This query will return all rows from tableA that do not have a corresponding row in tableB.

An Anti-Join is similar to the EXCEPT set operation but with key differences:

• In the EXCEPT operation, if at least one column is different between the two tables, the row is considered a difference and is kept.
• In the ANTI JOIN, we typically look at just whether the join keys are present in the other table or not. However, you can check as many columns as you want.

An example use case for a LEFT ANTI JOIN is finding all the products for which we have details (like product name) but do not have a row in the pricing table. This helps in identifying products that are missing pricing information.