如何在MySQL中对两个第一个字符求和

Question

是否可以在MySQL中使用SUBSTR和GROUP BY仅对前两个字符求和？
如：

SELECT SUM(Substr(period, 1,2) FROM table GROUP BY period

我已经尝试过这些SQL。但由于使用GROUP BY而没有效果。这些查询的结果是所有期间值的总和。

Answer 1

试试这个（如果你想对前两个字符求和）：

SELECT
    SUM(CAST(Substr(period, 1, 1)) AS int) + CAST(Substr(period, 2, 1)) AS int))
FROM
    table
GROUP BY
    period

或

SELECT
    SUM(CAST(Substr(Period, 1, 2) AS int)) 
FROM
    table
GROUP BY
    period

Answer 2

您可以改用字符ASCII值：

SELECT
    ASCII(Substr(period, 1,1)) + ASCII(Substr(period, 2, 1))
FROM
    test group by period;