![]() In the table has the same value as a new row for a The one below basically finds the first match from the left and then replaces all occurences of it (tested in mysql-5.6).12.2.7. How to get all distinct words of a specified minimum length from multiple columns in a MySQL table?.How to replace every other instance of a particular character in a MySQL.How to remove all non-alpha numeric characters from a string in. ![]() How to extract two consecutive digits from a text field in.How to extract the nth word and count word occurrences in a MySQL.How to count words in MySQL / regular expression.The function has been used to answer the following StackOverflow questions: Combining greedy and lazy matching within a single regular expression (e.g. There is a "greedy" flag to specify whether the overall matching should be greedy or non-greedy.patterns such as (^start|end$) are not supported. If ^and/or $ is used in the pattern, they must be at the very start and very end respectively - e.g.If this functionality is needed, please see this answer which attempts to provide a workaround by updating the function to allow a secondary find and replace within each found match (at the expense of increased complexity). It won't allow substitution of backreferences (e.g.Update: Have now added minimum and maximum match length parameters for improved efficiency when these are known (zero = unknown/unlimited). This method is of course going to take a while when the subject.SET result = CONCAT(LEFT(subject, startPos), result) SET result = IF(startInc = 1, CONCAT(result, SUBSTRING(subject, startPos, 1)),ĬONCAT(SUBSTRING(subject, startPos, 1), result)) SET startPos = startPos + startInc * len SET subStr = SUBSTRING(subject, startPos, len) ĬONCAT(result, replacement), CONCAT(replacement, result)) SET startPos = CHAR_LENGTH(subject) - minMatchLen + 1, startInc = -1 ĪND startPos + maxMatchLen - 1 = 1 AND len CHAR_LENGTH(subject)) DO SET startPos = CHAR_LENGTH(subject) - maxMatchLen + 1, startInc = 1 to the min or max match length from the end (depending on "greedy" flag). pattern ends with $ but doesn't start with ^): Set start pos IF LEFT(pattern, 1) = '^' OR RIGHT(pattern, 1) '$' THEN Set start position to 1 if pattern starts with ^ or doesn't end with $. SET usePattern = IF (RIGHT(pattern, 1) = '$', usePattern, CONCAT(usePattern, '$')) SET usePattern = IF (LEFT(pattern, 1) = '^', pattern, CONCAT('^', pattern)) Set the pattern to use to match an entire string rather than part of a string ![]() SET minMatchLen = IF(minMatchLen IS NULL OR minMatchLen CHAR_LENGTH(subject), RETURNS VARCHAR(21845) DETERMINISTIC BEGINĭECLARE result, subStr, usePattern VARCHAR(21845) ĭECLARE startPos, prevStartPos, startInc, len, lenInc INT Replacement VARCHAR(21845), greedy BOOLEAN, minMatchLen INT, maxMatchLen INT) SELECT reg_replace(txt, '^* ', 'a', TRUE, 2, 0) FROM tbl ĬREATE FUNCTION reg_replace(subject VARCHAR(21845), pattern VARCHAR(21845), optional and can be set to 0 or NULL if not known/required) (minMatchLen and maxMatchLen are used to improve efficiency but are is TRUE for greedy matching or FALSE for non-greedy matching is the regular expression to match against is the string to look in for doing the replacements The following expands upon the function provided by Rasika Godawatte but trawls through all necessary substrings rather than just testing single characters:. UPDATE 1: Have now made this into a blog post: This renders reading on unnecessary unless you're constrained to using an earlier version. UPDATE 2: A useful set of regex functions including REGEXP_REPLACE have now been provided in MySQL 8.0. In addition, the REGEXP_INSTR(), REGEXP_REPLACE(), and REGEXP_SUBSTR() functions are available to find match positions and perform substring substitution and extraction, respectively. The REGEXP_LIKE() function performs regular expression matching in the manner of the REGEXP and RLIKE operators, which now are synonyms for that function. Regular expression support has been reimplemented using International Components for Unicode (ICU), which provides full Unicode support and is multibyte safe. ![]() Previously, MySQL used the Henry Spencer regular expression library to support regular expression operators ( REGEXP, RLIKE). If expr, pat, or repl is NULL, the return value is NULL. Replaces occurrences in the string expr that match the regular expression specified by the pattern pat with the replacement string repl, and returns the resulting string. With MySQL 8.0+ you could use natively REGEXP_REPLACE function. ![]()
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