Oracle / PLSQL: REGEXP_LIKE Condition

This Oracle tutorial explains how to use the Oracle REGEXP_LIKE condition (to perform regular expression matching) with syntax and examples.

* Not to be confused with the LIKE condition which performs simple pattern matching.

Description

The Oracle REGEXP_LIKE condition allows you to perform regular expression matching in the WHERE clause of a SELECT, INSERT, UPDATE, or DELETE statement.

Syntax

The syntax for the REGEXP_LIKE condition in Oracle/PLSQL is:

REGEXP_LIKE ( expression, pattern [, match_parameter ] )

Parameters or Arguments

expression

A character expression such as a column or field. It can be a VARCHAR2, CHAR, NVARCHAR2, NCHAR, CLOB or NCLOB data type.

pattern

The regular expression matching information. It can be a combination of the following:

Value Description

^ Matches the beginning of a string. If used with a match_parameter of 'm', it matches the start of a line anywhere within expression.

$ Matches the end of a string. If used with a match_parameter of 'm', it matches the end of a line anywhere within expression.

* Matches zero or more occurrences.

+ Matches one or more occurrences.

? Matches zero or one occurrence.

. Matches any character except NULL.

| Used like an "OR" to specify more than one alternative.

[ ] Used to specify a matching list where you are trying to match any one of the characters in the list.

[^ ] Used to specify a nonmatching list where you are trying to match any character except for the ones in the list.

( ) Used to group expressions as a subexpression.

{m} Matches m times.

{m,} Matches at least m times.

{m,n} Matches at least m times, but no more than n times.

\n n is a number between 1 and 9. Matches the nth subexpression found within ( ) before encountering \n.

[..] Matches one collation element that can be more than one character.

[::] Matches character classes.

[==] Matches equivalence classes.

\d Matches a digit character.

\D Matches a nondigit character.

\w Matches a word character.

\W Matches a nonword character.

\s Matches a whitespace character.

\S matches a non-whitespace character.

\A Matches the beginning of a string or matches at the end of a string before a newline character.

\Z Matches at the end of a string.

*? Matches the preceding pattern zero or more occurrences.

+? Matches the preceding pattern one or more occurrences.

?? Matches the preceding pattern zero or one occurrence.

{n}? Matches the preceding pattern n times.

{n,}? Matches the preceding pattern at least n times.

{n,m}? Matches the preceding pattern at least n times, but not more than m times.

match_parameter

Optional. It allows you to modify the matching behavior for the REGEXP_LIKE condition. It can be a combination of the following:

Value Description

'c' Perform case-sensitive matching.

'i' Perform case-insensitive matching.

'n' Allows the period character (.) to match the newline character. By default, the period is a wildcard.

'm' expression is assumed to have multiple lines, where ^ is the start of a line and $ is the end of a line, regardless of the position of those characters in expression. By default, expression is assumed to be a single line.

'x' Whitespace characters are ignored. By default, whitespace characters are matched like any other character.

Note

The REGEXP_LIKE condition uses the input character set to evaluate strings.

If you specify match_parameter values that conflict, the REGEXP_LIKE condition will use the last value to break the conflict.

If the match_parameter is omitted, the REGEXP_LIKE condition will use the case-sensitivity as determined by the NLS_SORT parameter.

See also the Oracle LIKE condition.

Example - Match on more than one alternative

The first Oracle REGEXP_LIKE condition example that we will look at involves using the | pattern.

Let's explain how the | pattern works in the Oracle REGEXP_LIKE condition. For example:

SELECT last_name

FROM contacts

WHERE REGEXP_LIKE (last_name, 'Anders(o|e|a)n');

This REGEXP_LIKE example will return all contacts whose last_name is either Anderson, Andersen, or Andersan. The | pattern tells us to look for the letter "o", "e", or "a".

Example - Match on beginning

Next, let's use the REGEXP_LIKE condition to match on the beginning of a string. For example:

SELECT last_name

FROM contacts

WHERE REGEXP_LIKE (last_name, '^A(*)');

This REGEXP_LIKE example will return all contacts whose last_name starts with 'A'.

Example - Match on end

Next, let's use the REGEXP_LIKE condition to match on the end of a string. For example:

SELECT last_name

FROM contacts

WHERE REGEXP_LIKE (last_name, '(*)n$');

This REGEXP_LIKE example will return all contacts whose last_name ends with 'n'.

Artículo: "Oracle / PLSQL: REGEXP_LIKE Condition" Publicado en https://www.techonthenet.com/ por TechOnTheNet.com. Consultado el 09/02/2024.

URL: https://www.techonthenet.com/oracle/regexp_like.php