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Oracle REGEXP_LIKE function
Oracle REGEXP_LIKE function allows regular expressions in the WHERE sentence in SELECT, INSERT, UPDATE or DELETE queries.
Syntax for REGEXP_LIKE in Oracle/PLSQL
REGEXP_LIKE ( expression_id, pattern_id [, match_parameter _id] )
Parameters and function arguments
- expression – a symbolic expression such as a column or field. These can be the following data types: VARCHAR2, CHAR, NVARCHAR2, NCHAR, CLOB or NCLOB.
The pattern is a template. Regular expression for comparison. It can be a combination of the following values:
| Meaning | Description |
|---|---|
| ^ | Corresponds to the beginning of the line. When using match_parameter with ‘m’, it corresponds to the beginning of the string anywhere within the expression. |
| $ | Corresponds to the end of the line. When using match_parameter with ‘m’, it corresponds to the end of the string anywhere within the expression. |
| * | Corresponds to zero or more occurrences. |
| + | Corresponds to one or more occurrences. |
| ? | Corresponds to zero or one entry. |
| . | Corresponds to any character except NULL. |
| | | Used as “OR” to specify more than one alternative. |
| [ ] | It is used to specify a list of matches where you try to match any of the characters in the list. |
| [^ ] | It is used to specify a nonmatching list where you try to match any character except for those on the list. |
| ( ) | Used for group expressions as subexpressions. |
| {m} | Corresponds m times. |
| {m,} | Matching at least m times. |
| {m,n} | Matching at least m times, but not more than n times. |
| \n | n is a number between 1 and 9. It corresponds to the n-th subexpression located in ( ) before \n. |
| [..] | Corresponds to a single element mappings that can be more than one character. |
| [::] | Meets the symbol class. |
| [==] | Corresponds to the class of equivalence. |
| \d | Corresponds to the digital symbol. |
| \D | Corresponds to a non-digital symbol. |
| \w | Corresponds to the text symbol. |
| \W | Corresponds to a non-text symbol. |
| \s | Corresponds to the space character. |
| \S | Doesn’t match the space character. |
| \A | Corresponds to the beginning of a line or corresponds to the end of a line before a new line character. |
| \Z | Corresponds to the end of the line. |
| *? | Corresponds to the previous pattern of zero or more occurrences. |
| +? | One or more entries correspond to the previous template. |
| ?? | Corresponds to the previous zero or one entry pattern. |
| {n}? | Corresponds to the previous template n times. |
| {n,}? | Corresponds to the previous template at least n times. |
| {n,m}? | Corresponds to the previous template at least n times, but not more than m times. |
- match_parameter_id – Optional. This allows you to change the compliance behavior for the REGEXP_LIKE condition. This can be a combination of the following values:
| Meaning | Description |
|---|---|
| ‘c’ | Performs register-sensitive alignment. |
| ‘i’ | Performs case insensitive alignment. |
| ‘n’ | Allows a character period (.) to match the character of a new string. By default, the metasymic period. |
| ‘m’ | The expression assumes that there are several lines where ^ is the beginning of a line and $ is the end of a line, regardless of the position of these characters in the expression. By default, the expression is assumed to be on the same line. |
| ‘x’ | The symbols of spaces are ignored. By default, the space characters are the same as any other character. |
Note:
- The condition REGEXP_LIKE uses an input character set for string evaluation.
- If you specify match_parameter as a conflict, the REGEXP_LIKE condition will use the last value to break the conflict.
- If match_parameter is omitted, the condition REGEXP_LIKE will use case sensitivity as defined by parameter NLS_SORT.
Example of matching with more than one alternative
The first Oracle example of the REGEXP_LIKE condition, which we will consider, involves using the | template.
Let us explain how | template works in Oracle condition REGEXP_LIKE. For example:
SELECT last_name
FROM contacts
WHERE REGEXP_LIKE (last_name, 'Anders(o|e|a)n');
This example REGEXP_LIKE returns all contacts whose last_name is either ‘Anderson’, ‘Andersen’ or ‘Andersan’. The | template indicates that the search should be done with an “o”, “e”, or “a”.
Example of a start match
Next, we use the condition REGEXP_LIKE to match the beginning of the string. For example:
SELECT last_name
FROM contacts
WHERE REGEXP_LIKE (last_name, '^A(*)');
This example REGEXP_LIKE returns all the contacts whose last_name starts with ‘A’.
Example of end matching
Next, we use the condition REGEXP_ LIKE to match the end of the string. For example:
SELECT last_name
FROM contacts
WHERE REGEXP_LIKE (last_name, '(*)n$');
This example REGEXP_LIKE will return all the contacts whose last_name ends in ‘n’.
SQL for Beginners – Oracle regular expression: REGEXP_LIKE
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