mysql求100-999的水仙花数

在MySQL中，你可以使用嵌套循环和数学运算直接查询100到999之间的水仙花数。这里有一个简单的方式来实现这个查询：

SELECT num
FROM (
    SELECT 100 + 10 * x + y AS num
    FROM (SELECT 0 as x UNION ALL SELECT 1 as x UNION ALL SELECT 2 as x) t1,
         (SELECT 0 as y UNION ALL SELECT 1 as y UNION ALL SELECT 2 as y) t2
) subquery
WHERE num = (
    SELECT num
    FROM (
        SELECT 100 * x + 10 * y + z AS num
        FROM (SELECT 0 as x UNION ALL SELECT 1 as x UNION ALL SELECT 2 as x) t1,
             (SELECT 0 as y UNION ALL SELECT 1 as y UNION ALL SELECT 2 as y) t2,
             (SELECT 0 as z UNION ALL SELECT 1 as z UNION ALL SELECT 2 as z) t3
    ) subquery2
    WHERE num = num - POWER(num % 10, 3) - POWER(FLOOR(num / 10) % 10, 3) - POWER(FLOOR(num / 100), 3)
);

这个查询首先生成100到999的所有数字，然后通过`WHERE`条件检查每个数是否满足水仙花数的条件：各个位上的数字分别立方后之和等于原数。