Mysql -将一个数字拆分为单独的列，然后按每个单独的列对其求和

SELECT 
    SUBSTRING('123456', 1, 1) AS digit1,
    SUBSTRING('123456', 2, 1) AS digit2,
    SUBSTRING('123456', 3, 1) AS digit3,
    SUBSTRING('123456', 4, 1) AS digit4,
    SUBSTRING('123456', 5, 1) AS digit5,
    SUBSTRING('123456', 6, 1) AS digit6;

+--------+--------+--------+--------+--------+--------+
| digit1 | digit2 | digit3 | digit4 | digit5 | digit6 |
+--------+--------+--------+--------+--------+--------+
|      1 |      2 |      3 |      4 |      5 |      6 |
+--------+--------+--------+--------+--------+--------+

SELECT 
    SUM(digit1) AS sum1,
    SUM(digit2) AS sum2,
    SUM(digit3) AS sum3,
    SUM(digit4) AS sum4,
    SUM(digit5) AS sum5,
    SUM(digit6) AS sum6
FROM (
    SELECT 
        SUBSTRING('123456', 1, 1) AS digit1,
        SUBSTRING('123456', 2, 1) AS digit2,
        SUBSTRING('123456', 3, 1) AS digit3,
        SUBSTRING('123456', 4, 1) AS digit4,
        SUBSTRING('123456', 5, 1) AS digit5,
        SUBSTRING('123456', 6, 1) AS digit6
) AS digits;

+------+------+------+------+------+------+
| sum1 | sum2 | sum3 | sum4 | sum5 | sum6 |
+------+------+------+------+------+------+
|    1 |    2 |    3 |    4 |    5 |    6 |
+------+------+------+------+------+------+