我如何使用T-SQL的Case/When？

CASE
    WHEN condition1 THEN result1
    WHEN condition2 THEN result2
    ...
    ELSE resultN
END

SELECT
    employee_id,
    salary,
    CASE
        WHEN salary < 10000 THEN salary * 0.1
        WHEN salary >= 10000 AND salary < 20000 THEN salary * 0.15
        ELSE salary * 0.2
    END AS tax_amount
FROM
    employees;