sql - SQL Server - 计算两个字符之间的字符

Question

如何计算两个字符之间的字母数（按字母顺序从 a 到 z 或 z 到 a）？

例如：

WITH    ExampleData
          AS ( SELECT   'a' AS StartChar, 'e' AS EndChar
               UNION ALL
               SELECT   'm', 'r'
               UNION ALL
               SELECT   'f', 'a'
             )
    SELECT  StartChar ,
            EndChar
    FROM    ExampleData

需要生产：

StartChar   EndChar    Diff
a           e          4
m           r          5
f           a          -5

我看到如何使用 udf 和 while 循环轻松完成此操作，但我想知道是否有更快的方法？

Answer 1

SELECT StartChar, EndChar, ASCII(EndChar) - ASCII(StartChar) AS Diff
FROM ExampleData

SQL 小提琴示例

Answer 2

假设您已经对 StartChar 和 EndChar 进行了有效性检查...

SELECT ASCII(EndChar) - ASCII(StartChar) as Diff

Answer 3

这应该可以为您完成工作：

WITH    ExampleData
          AS ( SELECT   'a' AS StartChar, 'e' AS EndChar
               UNION ALL
               SELECT   'm', 'r'
               UNION ALL
               SELECT   'f', 'a'
             )
    SELECT  StartChar ,
            EndChar, ascii(EndChar) - ascii(StartChar) as Diff
    FROM    ExampleData

Answer 4

CTE真是太棒了！如果您不想使用 ASCII，那么您可以这样做：

;   With    CharCodes   (
    Code
)   As          (
    Select  65
Union   All
    Select  Code
    +   1
        From    CharCodes
        Where   Code        <   90
)
    Select  Second.Code
    -   First.Code
        From    CharCodes   As  First
        ,   CharCodes   As  Second
        Where   First.Code  =   Convert(Int, Convert(VarBinary, 'A'))
        And Second.Code =   Convert(Int, Convert(VarBinary, 'E'))

使用 ASCII 函数，您可以这样做：

Select  ASCII('E')
-   ASCII('A')