DECLARE @Variable INT;
SET @Variable = 1;

SELECT
    CASE
        WHEN @Variable = 1 OR @Variable = 2 THEN 'It is 1 or 2'
        WHEN @Variable = 3 THEN 'It is 3'
        ELSE 'It is not 1, 2, or 3'
    END AS [SomeField]

案例，或和表达式