SQL 返回列中的所有大写值

Question

我的字段值混合了大写和小写字符。 我试图只返回大写值作为一个结果，同样只返回另一个结果中的小写值。我不是想将一个转换为另一个，只是按原样返回当前数据。

我似乎找不到执行此操作的语句，“SUBSTRING”只会返回我指定的值，即第一个和最后一个字符

例如，如果我有 AAbbCCdd 并且想要返回大写值，我需要的结果是 AACC。

Answer 1

有一个功能：

CREATE FUNCTION [dbo].[GetCased](@BUFFER VARCHAR(MAX), @GETUPPER BIT) RETURNS VARCHAR(MAX) AS
BEGIN
    DECLARE @LEN INT = LEN(@BUFFER), @POS INT = 1, @CHAR CHAR(1), @RESULT VARCHAR(MAX) = ''
    WHILE @POS <= @LEN BEGIN
        SET @CHAR = SUBSTRING(@BUFFER, @POS, 1)
        SET @RESULT += CASE WHEN @CHAR COLLATE Latin1_General_CS_AS = 
            CASE WHEN @GETUPPER = 1 THEN UPPER(@CHAR) ELSE LOWER(@CHAR) END COLLATE Latin1_General_CS_AS THEN @CHAR ELSE '' END
        SET @POS += 1
    END
    RETURN @RESULT
END

... 

select
  dbo.GetCased('AAbbCCdd', 1) as 'all upper',
  dbo.GetCased('AAbbCCdd', 0) as 'all lower'

或者

CREATE FUNCTION [dbo].[fnRemovePatternFromString](@BUFFER VARCHAR(MAX), @PATTERN VARCHAR(128)) RETURNS VARCHAR(MAX) AS
BEGIN
    DECLARE @POS INT = PATINDEX(@PATTERN, @BUFFER COLLATE Latin1_General_CS_AS)
    WHILE @POS > 0 BEGIN
        SET @BUFFER = STUFF(@BUFFER, @POS, 1, '')
        SET @POS = PATINDEX(@PATTERN, @BUFFER COLLATE Latin1_General_CS_AS)
    END
    RETURN @BUFFER
END

...

select
  dbo.fnRemovePatternFromString('AAbbCCdd ', '%[ABCDEFGHIJKLMNOPQRSTUVWXYZ]%') as 'all lower'
  dbo.fnRemovePatternFromString('AAbbCCdd ', '%[abcdefghijklmnopqrstuvwxyz]%') as 'all upper'

（不能使用 [a-z]）

Answer 2

这是使用函数的另一种方式：

CREATE FUNCTION [dbo].returnUppers
    (
      @str AS varchar(Max)
    )
RETURNS varchar(MAX)
AS
    BEGIN
        DECLARE @len INT
        DECLARE @cc INT = 1
        DECLARE @return VARCHAR(MAX) = ''

        SELECT @len = LEN(@str)

        WHILE @len >= @cc
            BEGIN
                IF UPPER(SUBSTRING(@str,@cc,1)) = SUBSTRING(@str,@cc,1) COLLATE sql_latin1_general_cp1_cs_as
                    SELECT @return = @return + SUBSTRING(@str,@cc,1)
                SET @cc += 1
            END

        RETURN @return
    END
GO

使用方法：

DECLARE @string VARCHAR(20) = 'AAbbCCdd'
SELECT dbo.returnUppers(@string)

返回 AACC。您需要为 lowers 编写类似的函数，只需将 UPPER() 更改为 LOWER()

Answer 3

正如 cmets 中提到的 - 这应该在表示层中完成，而不是在 SQL 中。

不过，这并不妨碍它变得有趣！

关键是使用区分大小写的排序规则。在此示例中，我选择了 SQL_Latin1_General_CP1_CS_AS（“CS”=CaseSensitive。“CI”=CaseInsensitive）

虽然解决方案涉及循环（在这种情况下为递归 CTE），但您永远不会在这种事情上获得良好的性能

DECLARE @t table (
   a char(10)
);

INSERT INTO @t (a)
  VALUES ('AbC')
       , ('ABCDEFGHIJ')
       , ('aBCdEFghij')
       , ('AbcdefhhiJ')
       , ('ABcdEFGhij')
;

--SELECT a
--     , a COLLATE SQL_Latin1_General_CP1_CS_AS As case_sensitive_collation
--     , Replace(a COLLATE SQL_Latin1_General_CP1_CS_AS, 'A', '#') As case_sensitive_replace
--FROM   @t
--;

; WITH characters_to_replace AS (
  SELECT number
       , Char(number) As c
       , Row_Number() OVER (ORDER BY number) As sequence
  FROM   dbo.numbers
  WHERE  number BETWEEN 1 AND 255 -- basic characters
  AND    number NOT BETWEEN 65 AND 90 -- Exclude capital A-Z
)
, replacements AS (
SELECT a As original_value
     , Cast(a COLLATE SQL_Latin1_General_CP1_CS_AS As nvarchar(max)) As new_value
     , Cast(0 As bigint) As sequence
FROM   @t

  UNION ALL

    SELECT replacements.original_value
         , Cast(Replace(replacements.new_value, characters_to_replace.c, '') As nvarchar(max))
         , characters_to_replace.sequence
    FROM   replacements
     INNER
      JOIN characters_to_replace
        ON characters_to_replace.sequence = replacements.sequence + 1
)
SELECT original_value
     , new_value
FROM   replacements
WHERE  sequence = (SELECT Max(sequence) FROM characters_to_replace)
OPTION (MaxRecursion 255)
;