character_class « Regular Expressions « MySQL Tutorial

24.6.1.[:character_class:] represents a character class that matches all characters belonging to that class
24.6.2.'[[:alnum:]]' -- Alphanumeric characters
24.6.3.[[:alpha:]] -- Alphabetic characters
24.6.4.[[:blank:]] -- Whitespace characters
24.6.5.'[[:cntrl:]]' -- Control characters
24.6.6.'[[:digit:]]' -- Digit characters
24.6.7.'[[:graph:]]' -- Graphic characters
24.6.8.'[[:lower:]]' -- Lowercase alphabetic characters
24.6.9.'[[:print:]]' -- Graphic or space characters

24.6.10.'[[:punct:]]' -- Punctuation characters
24.6.11.'[[:space:]]' -- Space, tab, newline, and carriage return
24.6.12.'[[:upper:]]' -- Uppercase alphabetic characters
24.6.13.'[[:xdigit:]]' -- Hexadecimal digit characters