Regular Expressions +-----------------------------------+ mysql>  SELECT REGEXP_REPLACE(’abc def ghi’, ’[a-z]+’, ’X’, 1, 3); +----------------------------------------------------+ | REGEXP_REPLACE(’abc def ghi’, ’[a-z]+’, ’X’, 1, 3) | +----------------------------------------------------+ | abc def X | +----------------------------------------------------+ mysql>  SELECT REGEXP_SUBSTR(’abc def ghi’, ’[a-z]+’); +----------------------------------------+ | REGEXP_SUBSTR(’abc def ghi’, ’[a-z]+’) | +----------------------------------------+ | abc | +----------------------------------------+ mysql>  SELECT REGEXP_SUBSTR(’abc def ghi’, ’[a-z]+’, 1, 3); +----------------------------------------------+ | REGEXP_SUBSTR(’abc def ghi’, ’[a-z]+’, 1, 3) | +----------------------------------------------+ | ghi | +----------------------------------------------+ • REGEXP_SUBSTR( expr ,  pat [,  pos [,  occurrence [,  match_type ]]]) • pos : The position in  expr  at which to start the search. If omitted, the default is 1. • occurrence : Which occurrence of a match to search for. If omitted, the default is 1. • match_type : A string that specifies how to perform matching. The meaning is as described for REGEXP_LIKE() . Returns the substring of the string  expr  that matches the regular expression specified by the pattern pat ,  NULL  if there is no match. If  expr  or  pat  is  NULL , the return value is  NULL . REGEXP_SUBSTR()  takes these optional arguments: Prior to MySQL 8.0.17, the result returned by this function used the  UTF-16  character set; in MySQL 8.0.17 and later, the character set and collation of the expression searched for matches is used. (Bug #94203, Bug #29308212) For additional information about how matching occurs, see the description for  REGEXP_LIKE() . A regular expression describes a set of strings. The simplest regular expression is one that has no special characters in it. For example, the regular expression  hello  matches  hello  and nothing else. Nontrivial regular expressions use certain special constructs so that they can match more than one string. For example, the regular expression  hello|world  contains the  |  alternation operator and matches either the  hello  or  world . As a more complex example, the regular expression  B[an]*s  matches any of the strings  Bananas , Baaaaas ,  Bs , and any other string starting with a  B , ending with an  s , and containing any number of  a  or  n characters in between. The following list covers some of the basic special characters and constructs that can be used in regular expressions. For information about the full regular expression syntax supported by the ICU library used to implement regular expression support, visit the International Components for Unicode website. Regular Expression Syntax • ^ Match the beginning of a string. 2195