A. SELECT CAST(CHOOSE((Quarterly * AvailableBonus * CompanyPerformance)/40, (HalfYearly * AvailableBonus * CompanyPerformance)/20, (Yearly * AvailableBonus * CompanyPerformance)/10) AS money) AS Bonus
FROM EmployeeBonus, BonusParameters

B. SELECT
    Bonus = CASE EmployeeBonus
        WHEN Quarterly=1 THEN (Quarterly * AvailableBonus * CompanyPerformance)/40
        WHEN HalfYearly=1 THEN (HalfYearly * AvailableBonus * CompanyPerformance)/20
        WHEN Yearly=1 THEN (Yearly * AvailableBonus * CompanyPerformance)/10
    END
FROM EmployeeBonus,BonusParameters

C. SELECT
    CAST(COALESCE((Quarterly * AvailableBonus * CompanyPerformance)/40, (HalfYearly * AvailableBonus * CompanyPerformance)/20, (Yearly * AvailableBonus * CompanyPerformance)/10) AS money) AS Bonus
    FROM EmployeeBonus, BonusParameters

D. SELECT
    NULLIF(
        NULLIF((Quarterly * AvailableBonus * CompanyPerformance)/40,(HalfYearly * AvailableBonus * CompanyPerformance)/20),
         (Yearly * AvailableBonus * CompanyPerformance)/10) AS Bonus
    FROM EmployeeBonus, BonusParameters