Description of the MySQL regular expression

The mysql| Regular expression (regex) is a powerful tool for defining complex queries.
Here is a simple information that ignores some of the detailed information.
A regular expression defines a rule for a string. The simplest regular expression does not contain any reserved words. For example, the regular expression Hello is only matched to the string "Hello".
A regular expression uses some special structure, so it can match more strings. For example, regular expression Hello|word can match both the string "Hello" and the string "word". To give a more complicated example, the regular expression b[an]*s can match the string "Bananas", "Baaaaas", "Bs", and any other string that begins with B with the end of S, and the middle can include any combination of a and any n.

The following reserved words can be used in a regular expression
^
The matched string starts with the following string
mysql> Select "Fonfo" REGEXP "^fo$"; -> 0 (indicates no match)
mysql> Select "Fofo" REGEXP "^FO"; -> 1 (matching)
$
The matched string ends with the preceding string
Mysql> Select "Fono" REGEXP "^fono$"; -> 1 (matching)
Mysql> Select "Fono" REGEXP "^fo$"; -> 0 (indicates no match)
.
Match any character (including new rows)
mysql> Select "Fofo" REGEXP "^f.*"; -> 1 (matching)
mysql> Select "Fonfo" REGEXP "^f.*"; -> 1 (matching)
A *
Match any number of a (including empty strings)
mysql> Select "Ban" REGEXP "^ba*n"; -> 1 (matching)
mysql> Select "Baaan" REGEXP "^ba*n"; -> 1 (matching)
mysql> Select "Bn" REGEXP "^ba*n"; -> 1 (matching)
A +
Match any number of a (excluding empty strings)
mysql> Select "Ban" REGEXP "^ba+n"; -> 1 (matching)
mysql> Select "Bn" REGEXP "^ba+n"; -> 0 (indicates no match)
A?
Match one or 0 a
mysql> Select "Bn" REGEXP "^ba?n"; -> 1 (matching)
mysql> Select "Ban" REGEXP "^ba?n"; -> 1 (matching)
mysql> Select "Baan" REGEXP "^ba?n"; -> 0 (indicates no match)
De|abc
Match de or ABC
mysql> Select "PI" REGEXP "Pi|apa"; -> 1 (matching)
Mysql> select "Axe" REGEXP "Pi|apa"; -> 0 (indicates no match)
Mysql> Select "APA" REGEXP "Pi|apa"; -> 1 (matching)
Mysql> Select "APA" REGEXP "^ (Pi|apa) $"; -> 1 (matching)
mysql> Select "PI" REGEXP "^ (Pi|apa) $"; -> 1 (matching)
mysql> select "Pix" REGEXP "^ (Pi|apa) $"; -> 0 (indicates no match)
(ABC) *
Match any number of ABC (including Empty strings)
mysql> Select "PI" REGEXP "^ (pi) *$"; -> 1 (matching)
mysql> Select "Pip" REGEXP "^ (pi) *$"; -> 0 (indicates no match)
mysql> Select "Pipi" REGEXP "^ (pi) *$"; -> 1 (matching)
{1}
{2,3}
This is a more comprehensive approach that enables you to implement several of the previous reserved words
A *
Can be written as a{0,}
A +
Can be written as A{1,}
A?
Can be written as a{0,1}
There is only one integer parameter I in {}, which indicates that the character can only appear I; there is an integer parameter I in {}. followed by a ",", indicating that the character can appear I or I more than, in {} Only an integer parameter I, followed by a ",", and then an integer parameter J, indicating that the character can only appear more than I, J Times below (including I and J times). The integer argument must be greater than or equal to 0, and less than or equal to Re_dup_max (default is 255). If there are two parameters, the second must be greater than or equal to the first
[A-DX]
Match "A", "B", "C", "D" or "X"
[^A-DX]
Matches any character other than "A", "B", "C", "D", "X". "[", "]" must be used in pairs
mysql> Select "AxBC" REGEXP "[a-dxyz]"; -> 1 (matching)
mysql> Select "AxBC" REGEXP "^[a-dxyz]$"; -> 0 (indicates no match)
mysql> Select "AxBC" REGEXP "^[a-dxyz]+$"; -> 1 (matching)
mysql> Select "AxBC" REGEXP "^[^a-dxyz]+$"; -> 0 (indicates no match)
mysql> Select "Gheis" REGEXP "^[^a-dxyz]+$"; -> 1 (matching)
mysql> Select "Gheisa" REGEXP "^[^a-dxyz]+$"; -> 0 (indicates no match)
------------------------------------------------------------
[[. characters.]]
Represents the order in which elements are compared. The order of characters within parentheses is unique. But the parentheses can contain wildcards, so he can match more characters. For example: Regular expressions [[. Ch.]] *c matches the first five characters of the CHCHCC.
[=character_class=]
A class that represents equality and can replace other equal elements in a class, including itself. For example, if O and (+) are members of an equal class, then [[=o=]], [[= (+] =]] and [O (+)] are completely equivalent.
[: Character_class:]
Inside the brackets, in [: And:] The middle is the name of the character class, which can represent all characters belonging to this class.
The names of the character classes are: alnum, digit, punct, alpha, graph, space, blank, lower, upper, cntrl, print, and Xdigit
mysql> Select "Justalnums" REGEXP "[: alnum:]]+"; -> 1 (matching)
mysql> Select "!!" REGEXP "[[: alnum:]]+"; -> 0 (indicates no match)
[[::]]
An empty string that matches the beginning and end of a word, and neither the beginning nor the end of the word is a character that is contained in alnum and cannot be underlined.
Mysql> Select "A word a" REGEXP "[[::]]"; -> 1 (matching)
Mysql> Select "A Xword a" REGEXP "[[::]]"; -> 0 (indicates no match)
Mysql> Select "Weeknights" REGEXP "^ (Wee|week) (knights|nights) $"; -> 1 (matching)