Oracle
From QED
| Quantifier | Description |
| * | Match 0 or more times |
| ? | Match 0 or 1 time |
| + | Match 1 or more times |
| {m} | Match exactly m times |
| {m,} | Match at least m times |
| {m, n} | Match at least m times but no more than n times |
| Character Class | Description |
| [:alpha:] | Alphabetic characters |
| [:lower:] | Lowercase alphabetic characters |
| [:upper:] | Uppercase alphabetic characters |
| [:digit:] | Numeric digits |
| [:alnum:] | Alphanumeric characters |
| [:space:] | Space characters (nonprinting), such as carriage return, newline, vertical tab, and form feed |
| [:punct:] | Punctuation characters |
| [:cntrl:] | Control characters (nonprinting) |
| [:print:] | Printable characters |
| Metacharacter | Description | |
| | | Alternation | Separates alternates, often used with grouping operator () |
| ( ) | Group | Groups subexpression into a unit for alternations, for quantifiers, or for backreferencing (see "<A HREF="#back">Backreferences</A>" section) |
| [char] | Character list | Indicates a character list; most metacharacters inside a character list are understood as literals, with the exception of character classes, and the ^ and - metacharacters |
The REGEXP_LIKE Operator
| Syntax | Description |
| REGEXP_LIKE(source_string, pattern [, match_parameter]) | source_string supports character datatypes (CHAR, VARCHAR2, CLOB, NCHAR, NVARCHAR2, and NCLOB but not LONG). The pattern parameter is another name for the regular expression. match_parameter allows optional parameters such as handling the newline character, retaining multiline formatting, and providing control over case-sensitivity. |
The REGEXP_INSTR Function
| Syntax | Description |
| REGEXP_INSTR(source_string, pattern [, start_position | This function looks for a pattern and returns the first position of the pattern. Optionally, you can indicate the start_position you want to begin the search. The occurrence parameter defaults to 1 unless you indicate that you are looking for a subsequent occurrence. The default value of the return_option is 0, which returns the starting position of the pattern; a value of 1 returns the starting position of the next character following the match. |
