如何替换字符串中的奇数模式? [英] How I can replace odd patterns inside a string?

问题描述

我正在用SQL创建一个临时过程，因为我有一个用markdown编写的表的值，因此它在Web浏览器中显示为呈现的HTML.(将markdown转换为HTML).

I'm in the process of creating a temporary procedure in SQL because I have a value of a table which is written in markdown, so it appear as rendered HTML in the web browser (markdown to HTML conversion).

该列的字符串当前如下所示:

String of the column currently look like this:

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我目前正在处理粗体和斜体文本.这意味着(对于粗体文本而言)我将需要将模式**的奇数N替换为<b>，将偶数替换为</b>.
我看到了 replace()，但是它对字符串.

I'm currently working with bold and italic text. This mean (in the case of bold text) I will need to replace odd N times the pattern**with<b>and even times with</b>.
I saw replace() but it perform the replacement on all the patterns of the string.

那么，仅当它是奇数还是偶数时，才如何替换子字符串?

So How I can replace a sub-string only if it is odd or only it is even?

更新: 有些人想知道我使用的是哪种架构，所以请看一下 如果需要，还可以添加一个额外的 :标记为HTML的超链接的markdown样式看起来并不那么简单.

One more extra if you want: The markdown style hyperlink to html hyperlink doesn't look so simple.

推荐答案

使用STUFF函数和简单的WHILE循环:

Using theSTUFFfunction and a simpleWHILEloop:

CREATE FUNCTION dbo.fn_OddEvenReplace(@text nvarchar(500), 
                                      @textToReplace nvarchar(10), 
                                      @oddText nvarchar(10), 
                                      @evenText nvarchar(500))
RETURNS varchar(max)
AS
BEGIN
    DECLARE @counter tinyint
    SET @counter = 1

    DECLARE @switchText nvarchar(10)
    WHILE CHARINDEX(@textToReplace, @text, 1) > 0
    BEGIN
        SELECT @text = STUFF(@text, 
                    CHARINDEX(@textToReplace, @text, 1), 
                    LEN(@textToReplace), 
                    IIF(@counter%2=0,@evenText,@oddText)),
                @counter = @counter + 1
    END
    RETURN @text
END

您可以像这样使用它:

SELECT dbo.fn_OddEvenReplace(column, '**', '<b>', '</b>')
FROM table

更新:

这被重写为SP:

CREATE PROC dbo.##sp_OddEvenReplace @text nvarchar(500), 
                                  @textToReplace nvarchar(10), 
                                  @oddText nvarchar(10), 
                                  @evenText nvarchar(10),
                                  @returnText nvarchar(500) output
AS
BEGIN
    DECLARE @counter tinyint
    SET @counter = 1

    DECLARE @switchText nvarchar(10)
    WHILE CHARINDEX(@textToReplace, @text, 1) > 0
    BEGIN
        SELECT @text = STUFF(@text, 
                    CHARINDEX(@textToReplace, @text, 1), 
                    LEN(@textToReplace), 
                    IIF(@counter%2=0,@evenText,@oddText)),
                @counter = @counter + 1
    END
    SET @returnText = @text
END
GO

并执行:

DECLARE @returnText nvarchar(500)
EXEC dbo.##sp_OddEvenReplace '**a** **b** **c**', '**', '<b>', '</b>', @returnText output

SELECT @returnText

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