Table 1: Anchoring Metacharacters
| Metacharacter | Description |
| ^ | Anchor the expression to the start of a line |
| $ | Anchor the expression to the end of a line |
Table 2: Quantifiers, or Repetition Operators
| 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 "Backreferences" 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 |
Table 5: The REGEXP_LIKE Operator
| Syntax | Description |
[, 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. |
Table 6: The REGEXP_INSTR Function
| Syntax | Description |
[, start_position [, occurrence [, return_option [, match_parameter]]]]) | 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. |
Table 7: Explanation of 5-digit + 4 Zip-Code Expression
| Syntax | Description |
| Empty space that must be matched | |
| [:digit:] | POSIX numeric digit class |
| ] | End of character list |
| {5} | Repeat exactly five occurrences of the character list |
| ( | Start of subexpression |
| - | A literal hyphen, because it is not a range metacharacter inside a character list |
| [ | Start of character list |
| [:digit:] | POSIX [:digit:] class |
| [ | Start of character list |
| ] | End of character list |
| {4} | Repeat exactly four occurrences of the character list |
| ) | Closing parenthesis, to end the subexpression |
| ? | The ? quantifier matches the grouped subexpression 0 or 1 time thus making the 4-digit code optional |
| $ | Anchoring metacharacter, to indicate the end of the line |
Table 8: The REGEXP_SUBSTR Function
| Syntax | Description |
[, position [, occurrence [, match_parameter]]]) | The REGEXP_SUBSTR function returns the substring that matches the pattern. |
Table 9: The REGEXP_REPLACE Function
| Syntax | Description |
[, replace_string [, position [,occurrence, [match_parameter]]]]) | This function replaces the matching pattern with a specified replace_string, allowing complex search-and-replace operations. |
Table 10: Backreference Metacharacter
| Metacharacter | Description | |
| \digit | Backslash | Followed by a digit between 1 and 9, the backslash matches the preceding digit-th parenthesized subexpression. (Note: The backslash has another meaning in regular expressions; depending on the context it can also mean the Escape character |
Table 11: Explanation of Pattern-Swap Regular Expression
| Regular-Expression Item | Description |
| ( | Start of first subexpression |
| . | Match any single character except a newline |
| * | Repetition operator, matches previous . metacharacter 0 to n times |
| ) | End of first subexpression; result of the match is captured in \1 (In this example, it's Ellen.) |
| Empty space that needs to be present | |
| ( | Start of the second subexpression |
| . | Match any single character except a newline |
| * | Repetition operator matches the previous . metacharacter 0 to n times |
| ) | End of second subexpression; result of this match is captured in \2 (In this example, it stores Hildi.) |
| Empty space | |
| ( | Start of third subexpression |
| . | Match any single character except a newline |
| * | Repetition operator matches . metacharacter 0 to n times |
| ) | End of third subexpression; result of this match is captured in \3 (In this example, it holds Smith.) |
Table 12: Explanation of the Social Security Number Regular Expression
| Regular-Expression Item | Description |
| ^ | Start of line character (Regular expression cannot have any leading characters before the match.) |
| ( | Start subexpression and list alternates separated by the | metacharacter |
| [ | Start of character list |
| [:digit:] | POSIX numeric digit class |
| ] | End of character list |
| {3} | Repeat exactly three occurrences of character list |
| - | A hyphen |
| [ | Start of character list |
| [:digit:] | POSIX numeric digit class |
| ] | End of character list |
| {2} | Repeat exactly two occurrences of character list |
| - | Another hyphen |
| [ | Start of character list |
| [:digit:] | POSIX numeric digit class |
| ] | End of character list |
| {4} | Repeat exactly four occurrences of character list |
| | | Alternation metacharacter; ends the first choice and starts the next alternate expression |
| [ | Start of character list |
| [:digit:] | POSIX numeric digit class. |
| ] | End of character list |
| {9} | Repeat exactly nine occurrences of character list |
| ) | Ending parenthesis, to close the subexpression group used for alternation |
| $ | Anchoring metacharacter, to indicate the end of the line; no extra characters can follow the pattern |
