如何在MySQL中彙總兩個第一個字符？

Question

是否有可能在MySQL中只使用SUBSTR和GROUP BY前兩個字符？
如：

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

我嘗試了這些SQL。但沒有效果，因爲使用GROUP BY。這些查詢的結果是總和所有的週期值。

Answer 1

試試這個（如果你想總結兩個第一字符）：

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

您可以使用字符的ASCII值來代替：

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