SQL替换函数里面的正则表达式模式？

Question

SELECT REPLACE('<strong>100</strong><b>.00 GB', '%^(^-?\d*\.{0,1}\d+$)%', '');

我想用上面的正则表达式替换数字的两个部分之间的任何标记,但它似乎不起作用.我不确定它是否是正则表达式语法是错误的,因为我尝试了更简单的一个,例如'%[^0-9]%'只是为了测试,但它也没有用.有谁知道我怎么能做到这一点？

Answer 1

您可以使用PATINDEX 查找模式(字符串)出现的第一个索引.然后使用STUFF将另一个字符串填充到匹配的模式(字符串)中.

循环遍历每一行.用你想要的东西替换每个非法字符.在您的情况下,将非数字替换为空白.如果在循环的当前单元格中有多个非法字符,则内循环.

DECLARE @counter int

SET @counter = 0

WHILE(@counter < (SELECT MAX(ID_COLUMN) FROM Table))
BEGIN  

    WHILE 1 = 1
    BEGIN
        DECLARE @RetVal varchar(50)

        SET @RetVal =  (SELECT Column = STUFF(Column, PATINDEX('%[^0-9.]%', Column),1, '')
        FROM Table
        WHERE ID_COLUMN = @counter)

        IF(@RetVal IS NOT NULL)       
          UPDATE Table SET
          Column = @RetVal
          WHERE ID_COLUMN = @counter
        ELSE
            break
    END

    SET @counter = @counter + 1
END

注意:虽然这很慢!拥有varchar列可能会产生影响.所以使用LTRIM RTRIM可能会有所帮助.无论如何,它很慢.

幸得此 StackOverflow的答案.

编辑信用也转到@srutzky

编辑(通过@Tmdean)这个答案可以适应更基于集合的解决方案,而不是一次做一行.它仍然会迭代单行中非数字字符数的最大值,因此它并不理想,但我认为在大多数情况下它应该是可接受的.

WHILE 1 = 1 BEGIN
    WITH q AS
        (SELECT ID_Column, PATINDEX('%[^0-9.]%', Column) AS n
        FROM Table)
    UPDATE Table
    SET Column = STUFF(Column, q.n, 1, '')
    FROM q
    WHERE Table.ID_Column = q.ID_Column AND q.n != 0;

    IF @@ROWCOUNT = 0 BREAK;
END;

如果在表中维护一个表示该字段是否已被清除的列,您还可以提高效率.(在我的示例中,NULL表示"未知",应该是列默认值.)

DECLARE @done bit = 0;
WHILE @done = 0 BEGIN
    WITH q AS
        (SELECT ID_Column, PATINDEX('%[^0-9.]%', Column) AS n
        FROM Table
        WHERE COALESCE(Scrubbed_Column, 0) = 0)
    UPDATE Table
    SET Column = STUFF(Column, q.n, 1, ''),
        Scrubbed_Column = 0
    FROM q
    WHERE Table.ID_Column = q.ID_Column AND q.n != 0;

    IF @@ROWCOUNT = 0 SET @done = 1;

    -- if Scrubbed_Column is still NULL, then the PATINDEX
    -- must have given 0
    UPDATE table
    SET Scrubbed_Column = CASE
        WHEN Scrubbed_Column IS NULL THEN 1
        ELSE NULLIF(Scrubbed_Column, 0)
    END;
END;

如果您不想更改模式,则很容易适应将中间结果存储在表值变量中,该变量将在最后应用于实际表.

Answer 2

在一般意义上,SQL Server不支持正则表达式,您不能在本机T-SQL代码中使用它们.

你可以写一个CLR函数来做到这一点.例如,请参见此处.

Answer 3

不是通过其唯一的位置剥离找到的角色,使用Replace(Column, BadFoundCharacter, '')可能会大大加快.此外,不是仅替换每列中下一个找到的一个坏字符,而是替换所有找到的字符.

WHILE 1 = 1 BEGIN
    UPDATE dbo.YourTable
    SET Column = Replace(Column, Substring(Column, PatIndex('%[^0-9.-]%', Column), 1), '')
    WHERE Column LIKE '%[^0-9.-]%'
    If @@RowCount = 0 BREAK;
END;

我相信这会比接受的答案更好,只是因为它的操作更少.还有其他方法也可能更快,但我现在没有时间去探索这些方法.

Answer 4

对于那些正在寻找高性能且简单的解决方案并愿意启用 CLR 的人：

create database TestSQLFunctions
go
use TestSQLFunctions
go
alter database TestSQLFunctions set trustworthy on

EXEC sp_configure 'clr enabled', 1
RECONFIGURE WITH OVERRIDE
go

CREATE ASSEMBLY [SQLFunctions]
AUTHORIZATION [dbo]
FROM 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WITH PERMISSION_SET = SAFE

go

CREATE FUNCTION RegexReplace(
    @input nvarchar(max),
    @pattern nvarchar(max),
    @replacement nvarchar(max)
) RETURNS nvarchar  (max)
AS EXTERNAL NAME SQLFunctions.[SQLFunctions.Regex].Replace; 

go

-- outputs This is a test 
select dbo.RegexReplace('This is a test 12345','[0-9]','')

DLL 的内容：