MySQL has a number of functions and operators that allow us to perform operations using regular expressions (regex). This article presents two operators and one function that enable us to find out if a string matches a regular expression specified by a given pattern.
These regex functions and operators are:
These are all basically equivalent, as the operators (the second two) are both synonyms of the function (the first one). In any case, you can see examples of all three in action below.
In MySQL, the MATCH() function performs a full-text search. It accepts a comma separated list of table columns to be searched.
The table/s must have a FULLTEXT index before you can do a full-text search against them (although boolean queries against a MyISAM search index can work — albeit slowly — even without a FULLTEXT index).
You can create a FULLTEXT index when creating the table (using the CREATE TABLE statement), or you can use the ALTER TABLE statement or the CREATE INDEX statement if the table already exists.
By default, the search is case-insensitive. To perform a case-sensitive search, use a case-sensitive or binary collation for the indexed columns.
In MySQL, the CHARACTER_LENGTH() function returns the length of a string, measured in characters.
CHARACTER_LENGTH() is a synonym for the CHAR_LENGTH() function.
In MySQL, you can use NOT LIKE to perform a negation of the LIKE operator. In other words, NOT LIKE returns the opposite result to LIKE.
If the string matches the pattern provided, the result is 0, otherwise it’s 1.
The pattern doesn’t necessarily need to be a literal string. This function can be used with string expressions and table columns.
In MySQL, the REGEXP_REPLACE() function replaces occurrences of the substring within a string that matches the given regular expression pattern.
The whole string is returned along with the replacements.
If there’s no match (i.e. the input string doesn’t contain the substring), the the whole string is returned unchanged.