OracleSQL使用if基于多个列强制转换新变量

CASE 列名
    WHEN 值1 THEN 结果1
    WHEN 值2 THEN 结果2
    ...
    ELSE 结果N
END

SELECT score,
    CASE score
        WHEN 90 THEN 'A'
        WHEN 80 THEN 'B'
        WHEN 70 THEN 'C'
        ELSE 'D'
    END AS grade
FROM table_name;

CASE
    WHEN 条件1 THEN 结果1
    WHEN 条件2 THEN 结果2
    ...
    ELSE 结果N
END

SELECT age, gender,
    CASE
        WHEN age < 18 AND gender = 'M' THEN '未成年男性'
        WHEN age < 18 AND gender = 'F' THEN '未成年女性'
        WHEN age >= 18 AND gender = 'M' THEN '成年男性'
        WHEN age >= 18 AND gender = 'F' THEN '成年女性'
        ELSE '未知'
    END AS description
FROM table_name;