使用CASE WHEN语句编写If -then do从SAS到SQL的代码

data example;
    set input_data;
    if age < 18 then category = 'Child';
    else if age >= 18 and age < 65 then category = 'Adult';
    else category = 'Senior';
run;

SELECT 
    *,
    CASE 
        WHEN age < 18 THEN 'Child'
        WHEN age >= 18 AND age < 65 THEN 'Adult'
        ELSE 'Senior'
    END AS category
FROM input_data;

SELECT 
    *,
    CASE 
        WHEN age < 18 THEN 'Child'
        WHEN age >= 18 AND age < 65 THEN 'Adult'
        ELSE 'Senior'
    END AS category
FROM input_data;

SELECT 
    *,
    CASE 
        WHEN age IS NULL THEN 'Unknown'
        WHEN age < 18 THEN 'Child'
        WHEN age >= 18 AND age < 65 THEN 'Adult'
        ELSE 'Senior'
    END AS category
FROM input_data;