MySQL： regexp_ replace

Command format ：
regexp_replace(source, pattern, replace_string, occurrence)
Parameter description ：
● source: string type , The original string to replace .
● pattern: string Type constant , The regular pattern to match ,pattern Throw an exception when the string is empty .
● replace_string:string, Will match pattern String replaced with .
● occurrence: bigint Type constant , Must be greater than or equal to 0,
Greater than 0： Means to replace the number of matches with replace_string,
be equal to 0： Means to replace all matching substrings .
Other types or less than 0 Throw exceptions .

 Common cases 
1、 use ’#‘ Replace all numbers in the string 
SELECT regexp_replace('01234abcde56789','[0-9]','#') AS new_str FROM dual;

 result ：#####abcde#####

 use ’#‘ Replace the number in the string 0、9
SELECT regexp_replace(‘01234abcde56789’,’[09]’,’#’) AS new_str FROM dual;

 result ：#1234abcde5678#

2、 Skip when encountering non lowercase letters or numbers , From match to 4 Values begin to replace , Replace with ''
SELECT regexp_replace('abcdefg123456ABC','[a-z0-9]','',4)

 result ：abcefg123456ABC

SELECT regexp_replace('abcDEfg123456ABC','[a-z0-9]','',4)

 result ：abcDEg123456ABC

SELECT regexp_replace('abcDEfg123456ABC','[a-z0-9]','',7);

 result ：abcDEfg13456ABC

 Skip when encountering non lowercase letters or numbers , Replace all matching values with ''
SELECT regexp_replace('abcDefg123456ABC','[a-z0-9]','',0);

 result ：DABC


3、 Format the phone number , take [phone] Convert to ([phone],’+‘ There are definitions in regular expressions , Need to escape .\\1 Represents the first group of references 
SELECT regexp_replace('[phone]','(\\+[0-9]{2})( )([0-9]{3})([0-9]{4})([0-9]{4})','(\\1)\\3-\\4-\\5',0);

 result ：([phone]

SELECT regexp_replace("123.456.7890","([[:digit:]]{3})\\.([[:digit:]]{3})\\.([[:digit:]]{4})","(\\1)\\2-\\3",0) ;
SELECT regexp_replace("123.456.7890","([0-9]{3})\\.([0-9]{3})\\.([0-9]{4})","(\\1)\\2-\\3",0) ;

 result ：[phone]


4、 Separate characters with spaces ,0 Means to replace all matching substrings .
      SELECT regexp_replace('abcdefg123456ABC','(.)','\\1 ',0) AS new_str FROM dual;

 result ：a b c d e f g 1 2 3 4 5 6 A B C

      SELECT regexp_replace('abcdefg123456ABC','(.)','\\1 ',2) AS new_str FROM dual;

 result ：ab cdefg123456ABC

5、
SELECT regexp_replace("abcd","(.*)(.)$","\\1",0) ;
 result ：abc

SELECT regexp_replace("abcd","(.*)(.)$","\\2",0) ;
 result ：d

SELECT regexp_replace("abcd","(.*)(.)$","\\1-\\2",0) ;
 result ：abc-d
 Other cases ：
SELECT regexp_replace("abcd","(.)","\\2",1)  The result is "abcd", because pattern Only one group is defined in , The second group referenced does not exist .
SELECT regexp_replace("abcd","(.*)(.)$","\\2",0)  The result is "d"
SELECT regexp_replace("abcd","(.*)(.)$","\\1",0)  The result is "abc"
SELECT regexp_replace("abcd","(.*)(.)$","\\1-\\2",0)  The result is "abc-d"
SELECT regexp_replace("abcd","a","\\1",0), The result is ” \1bcd”, Because in pattern There is no group definition in , therefore \1 Direct output to characters .