How Can SQL's CASE Statement Enable Conditional Filtering in the WHERE Clause?

Conditional Filtering in SQL's WHERE Clause Using CASE

SQL's WHERE clause is used for filtering data based on specified conditions. When you need to apply different filtering criteria depending on the data itself, the CASE statement within the WHERE clause provides a powerful and flexible approach.

Imagine a table containing various location types ("location," "area," "division") with their respective IDs stored in columns account_location, xxx_location_area, and xxx_location_division. To retrieve records based on the chosen location type, a CASE statement elegantly handles the conditional logic:

<code class="language-sql">DECLARE @locationType VARCHAR(50);
DECLARE @locationID INT;

SELECT column1, column2
FROM viewWhatever
WHERE
@locationID = CASE @locationType
                WHEN 'location' THEN account_location
                WHEN 'area' THEN xxx_location_area
                WHEN 'division' THEN xxx_location_division
                END;</code>

By setting the @locationID and @locationType variables appropriately, you can dynamically filter results. The CASE statement determines which location column to compare against @locationID, enabling efficient and adaptable conditional filtering.

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