| Metacharacters | Meaning | Examples |
| \ | Indicates that the match character is a special character, a literal, or a backreference. (A backreference repeats the previous match.) | \n matches the newline character,\\ matches \, \( matches (, \) matches ) |
| ^ | Matches the position at the start of the string. | ^A matches A if A is the first character in the string. |
| $ | Matches the position at the end of the string. | $B matches B if B is the last character in the string. |
| * | Matches the preceding character zero or more times. | ba*rk matches brk, bark, baark, and so on. |
| + | Matches the preceding character one or more times. | ba+rk matches bark, baark, and so on, but not brk. |
| ? | Matches the preceding character zero or one time. | ba?rk matches brk and bark only. |
| {n} | Matches a character exactly n times, where n is an integer. | hob{2}it matches hobbit. |
| {n,m} | Matches a character at least n times and at most m times, where n and m are both integers. | hob{2,3}it matches hobbit and hobbbit only. |
| . | Matches any single character except null. | hob.it matches hobait, hobbit, and so on. |
| (pattern) | A subexpression that matches the specified pattern. You use subexpressions to build up complex regular expressions. You can access the individual matches, known as captures, from this type of subexpression. | anatom(y|ies) matches anatomy and anatomies. |
| x|y | Matches x or y, where x and y are one or more characters. | war|peace matches war or peace. |
| [abc] | Matches any of the enclosed characters. | [ab]bc matches abc and bbc. |
| [a-z] | Matches any character in the specified range. | [a-c]bc matches abc, bbc, and cbc. |
| [: :] | Specifies a character class and matches any character in that class. | [:alphanum:] matches alphanumeric characters 0-9, A-Z, and a-z.[:alpha:] matches alphabetic characters A-Z and a-z.[:blank:] matches space or tab.[:digit:] matches digits 0-9.[:graph:] matches non-blank characters.[:lower:] matches lowercase alphabetic characters a-z.[:print:] is similar to [:graph:] except [:print:] includes the space character.[:punct:] matches punctuation characters .,"', and so on.[:space:] matches all whitespace characters.[:upper:] matches all uppercase alphabetic characters A-Z.[:xdigit:] matches characters permissible in a hexadecimal number 0-9, A-F, and a-f. |
| [..] | Matches one collation element, like a multicharacter element. | No example. |
| [==] | Specifies equivalence classes. | No example. |
| \n | This is a backreference to an earlier capture, where n is a positive integer. | (.)\1 matches two consecutive identical characters. The (.) captures any single character except null, and the \1 repeats the capture, matching the same character again, therefore matching two consecutive identical characters. |
Quote from:
Oracle Database 10g SQL (Osborne ORACLE Press Series) (Paperback)
# Paperback: 608 pages
# Publisher: McGraw-Hill Osborne Media; 1st edition (February 20, 2004)
# Language: English
# ISBN-10: 0072229810
# ISBN-13: 978-0072229813
| 18.1.Introduction | ||||
| 18.1.1. | Regular Expression Metacharacters | |||
| 18.1.2. | Regular Expression Functions | |||