SQL BETWEEN 与 CASE 语句

Question

我在使用案例陈述时遇到了一些困难。我需要在具有许多不同字符和条件的字段上运行一个 case 语句。我首先需要去除所有非数字值的字段，然后根据字段的值设置一个值，我已经能够编写一个 case 语句来执行此操作，但它非常慢。这有效：

CASE
WHEN (SELECT CAST(CAST((SELECT SUBSTRING(fieldtoreplace, Number, 1) FROM master..spt_values WHERE Type='p' AND Number <= LEN(fieldtoreplace) AND SUBSTRING(fieldtoreplace, Number, 1) LIKE '[0-9]' FOR XML Path('')) AS xml) AS varchar(255))) BETWEEN 1 and 10 THEN 'MIN'
WHEN (SELECT CAST(CAST((SELECT SUBSTRING(fieldtoreplace, Number, 1) FROM master..spt_values WHERE Type='p' AND Number <= LEN(fieldtoreplace) AND SUBSTRING(fieldtoreplace, Number, 1) LIKE '[0-9]' FOR XML Path('')) AS xml) AS varchar(255))) BETWEEN 11 and 25 THEN 'MID'
WHEN (SELECT CAST(CAST((SELECT SUBSTRING(fieldtoreplace, Number, 1) FROM master..spt_values WHERE Type='p' AND Number <= LEN(fieldtoreplace) AND SUBSTRING(fieldtoreplace, Number, 1) LIKE '[0-9]' FOR XML Path('')) AS xml) AS varchar(255))) = 26 THEN 'MAX'
ELSE 'UNKNOWN'
END

但是，我希望能够做一些更像下面的事情，它只运行转换一次，而不是对 case 语句的每一行进行转换。

CASE (SELECT CAST(CAST((SELECT SUBSTRING(fieldtoreplace, Number, 1) FROM master..spt_values WHERE Type='p' AND Number <= LEN(fieldtoreplace) AND SUBSTRING(fieldtoreplace, Number, 1) LIKE '[0-9]' FOR XML Path('')) AS xml) AS varchar(255)))
WHEN BETWEEN 1 and 10 THEN 'MIN'
WHEN BETWEEN 11 and 25 THEN 'MID'
WHEN 26 THEN 'MAX'
ELSE 'UNKNOWN'
END

实际语句是 41 种不同的情况，包含各种 between 和 equals 语句。

有没有人有这样做的解决方案，以便转换只需运行一次？ table 它是运行ning 反对是非常大的。

两者的输出应该是：

9    MIN
5    MIN
26   MAX
26   MAX
25   MID
44   UNKNOWN

Answer 1

在 SQL 服务器中，如果您不想多次运行某些内容，请使用 APPLY:

select . . .,
       (case when v.val between 1 and 10 then 'MIN'
             when v.val between 11 and 25 then 'MID'
             when v.val = 26 then 'MAX'
             else 'UNKNOWN'
        end    
from . . . CROSS APPLY
     (VALUES ( (SELECT CAST(CAST((SELECT SUBSTRING(fieldtoreplace, Number, 1) FROM master..spt_values WHERE Type='p' AND Number <= LEN(fieldtoreplace) AND SUBSTRING(fieldtoreplace, Number, 1) LIKE '[0-9]' FOR XML Path('')) AS xml) AS varchar(255)))
     ) v(val)

SQL BETWEEN 与 CASE 语句

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