在我的数据库中有包含大量内部链接的竞争区域。我必须将链接结构从 www.mydomain.de/page.html 更改为 www.mydomain.de/page/，但替换语句应尊重域:

这是预期要替换的内容:

www.mydomain.de/somepage.html -> www.mydomain.de/page/
www.mydomain.de/subfolder/page.html -> www.mydomain.de/subfolder/page/
www.mydomain.de/link.html?param=1 -> www.mydomain.de/page/?param=1
www.mydomain.de/another-link.html#hash -> www.mydomain.de/page/#hash

所有其他链接都应该保持不变，这里有一些例子，但可以是网络上的任何链接:

 www.some-domain.de/link.html    
 www.another-domain.com/somelink.html

一个内容字段中可以有不同的链接:

<p>If you want to read more, click 
<a href="http://www.mydomain.de/page.html">here</a> 
or there <a href="http://www.another-domain.com/somelink.html">there</a>

这是在做替换:

UPDATE tablename 
SET contentfield = REPLACE(contentfield, '.html', '/') 

我的想法(但不知道如何为他们创建一个声明):

• 在前 100 个字符中找到“mydomain.de”
• WHERE 找到的“.html”数量 = 找到的“mydomain.de”数量

不一定要 100% 匹配所有 'mydomain.de' 链接，我对 90% 很满意，但外部链接不应该有错误的替换。

最佳答案

更新:现在已将其制作成博客文章:http://stevettt.blogspot.co.uk/2018/02/a-mysql-regular-expression-replace.html

请查看以下 Rextester Fiddle，我认为它应该会产生您要求的所有结果:

Rextester Demo

解释

为此需要模式替换功能，但不幸的是 MySQL doesn't provide such a thing .所以我写了一个(基于另一个不够充分的)并发布了它 here .如引用的答案中所述，此函数有一个限制，即不允许用反向引用替换捕获组。因此，它在 fiddle 中被稍微修改以获取更多参数，允许它在找到的替换匹配项中执行递归替换。 (注意根据 this excellent answer 在正则表达式中使用允许的 URL 路径字符)。

更新 SQL

以下 SQL 将使用以下函数更新表数据:

UPDATE urls
SET url = reg_replace(
  url,
  'www\\.mydomain\\.de/[-A-Za-z0-9\\._~!\\$&''\\(\\)\\*\\+,;=:@%/]+\\.html',
  '/[^/]+\\.html',
  '/page/',
  TRUE,
  22, -- Min match length = www.mydomain.de/?.html = 22
  0,  -- No max match length
  7,  -- Min sub-match length = /?.html = 7
  0   -- No max sub-match length
  );

函数代码

下面也贴出了demo中使用的UDF代码。注意:自 only stored procedures will allow recursion in MySQL 以来，UDF 委托(delegate)给一个存储过程.

-- ------------------------------------------------------------------------------------
-- USAGE
-- ------------------------------------------------------------------------------------
-- SELECT reg_replace(<subject>,
--                    <pattern>,
--                    <subpattern>,
--                    <replacement>,
--                    <greedy>,
--                    <minMatchLen>,
--                    <maxMatchLen>,
--                    <minSubMatchLen>,
--                    <maxSubMatchLen>);
-- where:
-- <subject> is the string to look in for doing the replacements
-- <pattern> is the regular expression to match against
-- <subpattern> is a regular expression to match against within each
--              portion of text that matches <pattern>
-- <replacement> is the replacement string
-- <greedy> is TRUE for greedy matching or FALSE for non-greedy matching
-- <minMatchLen> specifies the minimum match length
-- <maxMatchLen> specifies the maximum match length
-- <minSubMatchLen> specifies the minimum match length
-- <maxSubMatchLen> specifies the maximum match length
-- (minMatchLen, maxMatchLen, minSubMatchLen and maxSubMatchLen are used to improve
--  efficiency but are optional and can be set to 0 or NULL if not known/required)
-- Example:
-- SELECT reg_replace(txt, '[A-Z0-9]{3}', '[0-9]', '_', TRUE, 3, 3, 1, 1) FROM tbl;
DROP FUNCTION IF EXISTS reg_replace;
DELIMITER //
CREATE FUNCTION reg_replace(subject VARCHAR(21845), pattern VARCHAR(21845),
  subpattern VARCHAR(21845), replacement VARCHAR(21845), greedy BOOLEAN,
  minMatchLen INT, maxMatchLen INT, minSubMatchLen INT, maxSubMatchLen INT)
RETURNS VARCHAR(21845) DETERMINISTIC BEGIN
  DECLARE result VARCHAR(21845);
  CALL reg_replace_worker(
    subject, pattern, subpattern, replacement, greedy, minMatchLen, maxMatchLen,
    minSubMatchLen, maxSubMatchLen, result);
  RETURN result;
END;//
DELIMITER ;

DROP PROCEDURE IF EXISTS reg_replace_worker;
DELIMITER //
CREATE PROCEDURE reg_replace_worker(subject VARCHAR(21845), pattern VARCHAR(21845),
  subpattern VARCHAR(21845), replacement VARCHAR(21845), greedy BOOLEAN,
  minMatchLen INT, maxMatchLen INT, minSubMatchLen INT, maxSubMatchLen INT,
  OUT result VARCHAR(21845))
BEGIN
  DECLARE subStr, usePattern, useRepl VARCHAR(21845);
  DECLARE startPos, prevStartPos, startInc, len, lenInc INT;
  SET @@SESSION.max_sp_recursion_depth = 2;
  IF subject REGEXP pattern THEN
    SET result = '';
    -- Sanitize input parameter values
    SET minMatchLen = IF(minMatchLen < 1, 1, minMatchLen);
    SET maxMatchLen = IF(maxMatchLen < 1 OR maxMatchLen > CHAR_LENGTH(subject),
                         CHAR_LENGTH(subject), maxMatchLen);
    -- Set the pattern to use to match an entire string rather than part of a string
    SET usePattern = IF (LEFT(pattern, 1) = '^', pattern, CONCAT('^', pattern));
    SET usePattern = IF (RIGHT(pattern, 1) = '$', usePattern, CONCAT(usePattern, '$'));
    -- Set start position to 1 if pattern starts with ^ or doesn't end with $.
    IF LEFT(pattern, 1) = '^' OR RIGHT(pattern, 1) <> '$' THEN
      SET startPos = 1, startInc = 1;
    -- Otherwise (i.e. pattern ends with $ but doesn't start with ^): Set start pos
    -- to the min or max match length from the end (depending on "greedy" flag).
    ELSEIF greedy THEN
      SET startPos = CHAR_LENGTH(subject) - maxMatchLen + 1, startInc = 1;
    ELSE
      SET startPos = CHAR_LENGTH(subject) - minMatchLen + 1, startInc = -1;
    END IF;
    WHILE startPos >= 1 AND startPos <= CHAR_LENGTH(subject)
      AND startPos + minMatchLen - 1 <= CHAR_LENGTH(subject)
      AND !(LEFT(pattern, 1) = '^' AND startPos <> 1)
      AND !(RIGHT(pattern, 1) = '$'
            AND startPos + maxMatchLen - 1 < CHAR_LENGTH(subject)) DO
      -- Set start length to maximum if matching greedily or pattern ends with $.
      -- Otherwise set starting length to the minimum match length.
      IF greedy OR RIGHT(pattern, 1) = '$' THEN
        SET len = LEAST(CHAR_LENGTH(subject) - startPos + 1, maxMatchLen), lenInc = -1;
      ELSE
        SET len = minMatchLen, lenInc = 1;
      END IF;
      SET prevStartPos = startPos;
      lenLoop: WHILE len >= 1 AND len <= maxMatchLen
                 AND startPos + len - 1 <= CHAR_LENGTH(subject)
                 AND !(RIGHT(pattern, 1) = '$' 
                       AND startPos + len - 1 <> CHAR_LENGTH(subject)) DO
        SET subStr = SUBSTRING(subject, startPos, len);
        IF subStr REGEXP usePattern THEN
          IF subpattern IS NULL THEN
            SET useRepl = replacement;
          ELSE
            CALL reg_replace_worker(subStr, subpattern, NULL, replacement, greedy, 
                          minSubMatchLen, maxSubMatchLen, NULL, NULL, useRepl);
          END IF;
          SET result = IF(startInc = 1,
                          CONCAT(result, useRepl), CONCAT(useRepl, result));
          SET startPos = startPos + startInc * len;
          LEAVE lenLoop;
        END IF;
        SET len = len + lenInc;
      END WHILE;
      IF (startPos = prevStartPos) THEN
        SET result = IF(startInc = 1, CONCAT(result, SUBSTRING(subject, startPos, 1)),
                        CONCAT(SUBSTRING(subject, startPos, 1), result));
        SET startPos = startPos + startInc;
      END IF;
    END WHILE;
    IF startInc = 1 AND startPos <= CHAR_LENGTH(subject) THEN
      SET result = CONCAT(result, RIGHT(subject, CHAR_LENGTH(subject) + 1 - startPos));
    ELSEIF startInc = -1 AND startPos >= 1 THEN
      SET result = CONCAT(LEFT(subject, startPos), result);
    END IF;
  ELSE
    SET result = subject;
  END IF;
END;//
DELIMITER ;

关于MySQL 替换给定域的 .html 链接，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/38541913/