SQL Server - Coalesce

Scenario

If you want to pick a column from TableA, but if it’s NULL, use a column from TableB, you need to use the COALESCE built-in function in SQL Server.

Code

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SELECT
    COALESCE(a.ColumnName, b.ColumnName) AS PreferredColumn
FROM
    TableA a
JOIN
    TableB b ON a.ID = b.ID;

COALESCE returns the first non-null value from the list.

Documentation

Reference: Microsoft Learn.

Credits: Image from Microsoft Server