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MySQL替换给定域的.html链接
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内容图文
在我的数据库中有contenfields有很多内部链接.我必须将链接结构从www.mydomain.de/page.html更改为www.mydomain.de/page/,但是replace语句应该尊重域名：
这有望取代：
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
所有其他链接应该不受影响,这里有一些示例,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)：
>在前面的100个字符中找到’mydomain.de’的位置
>找到“.html”的数量=找到“mydomain.de”的数量
它不必100％匹配所有’mydomain.de’链接,我很满意90％,但外部链接不应该有错误的替换.
解决方法:
更新：现在已将其变成博客文章：http://stevettt.blogspot.co.uk/2018/02/a-mysql-regular-expression-replace.html
请参阅以下Rextester小提琴,我认为应该产生您要求的所有结果：
说明
这需要一个替换模式的功能,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)并发布了它here.如引用的答案所述,这个函数有一个不允许替换的限制捕获具有反向引用的组.因此,它在小提琴中稍微适应了进一步的参数,允许它在找到的替换匹配中执行递归替换. (注意在this excellent answer中使用正则表达式中允许的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
);
功能代码
演示中使用的UDF代码也发布在下面.注意：UDF从only stored procedures will allow recursion in MySQL开始委托存储过程.
-- ------------------------------------------------------------------------------------
-- 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 ;
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