To implement regular expression support in either SQL or PL/SQL, you use a new set of functions. These functions are:
| Function Name | Description |
| REGEXP_LIKE | Similar to the LIKE operator, but performs regular expression matching instead of simple pattern matching |
| REGEXP_INSTR | Searches for a given string for a regular expression pattern and returns the position were the match is found |
| REGEXP_REPLACE | Searches for a regular expression pattern and replaces it with a replacement string |
| REGEXP_SUBSTR | Searches for a regular expression pattern within a given string and returns the matched substring |
POSIX Metacharacters in Oracle Database Regular Expressions
Metacharacters are special characters that have a special meaning, such as a wild card character, a repeating character, a nonmatching character, or a range of characters.
You can use several predefined metacharacter symbols in the pattern matching with the functions.
| Symbol | Description |
* | Matches zero or more occurrences |
| | Alternation operator for specifying alternative matches |
^/$
| Matches the start of line and the end of line |
[] | Bracket expression for a matching list matching any one of the expressions represented in the list |
[^exp] | If the caret is inside the bracket, it negates the expression. |
{m} | Matches exactly m times |
{m,n} | Matches at least m times but no more than n times |
[: :] | Specifies a character class and matches any character in that class |
\ | Can have four different meanings: (1) stand for itself; (2) quote the next character; (3) introduce an operator; (4) do nothing |
+ | Matches one or more occurrences |
? | Matches zero or one occurrence |
. | Matches any character in the supported character set (except NULL) |
() | Grouping expression (treated as a single subexpression) |
\n | Backreference expression |
[==]
| Specifies equivalence classes |
[..]
| Specifies one collation element (such as a multicharacter element) |
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