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Oracle Regular Expressions
Version 11.1
 
General Information

Anchoring Characters
Character Class Description
^ Anchor the expression to the start of a line
$ Anchor the expression to the end of a line

Equivalence Classes
Character Class Description
= = Oracle supports the equivalence classes through the POSIX '[==]' syntax. A base letter and all of its accented versions constitute an equivalence class. For example, the equivalence class '[=a=]' matches ä and â. The equivalence classes are valid only inside the bracketed expression

Match Options
Character Class Description
c Case sensitive matching
i Case insensitive matching
m Treat source string as multi-line activating Anchor chars
n Allow the period (.) to match any newline character

Posix Characters
Character Class Description
[:alnum:] Alphanumeric characters
[:alpha:] Alphabetic characters
[:blank:] Blank Space Characters
[:cntrl:] Control characters (nonprinting)
[:digit:] Numeric digits
[:graph:] Any [:punct:], [:upper:], [:lower:], and [:digit:] chars
[:lower:] Lowercase alphabetic characters
[:print:] Printable characters
[:punct:] Punctuation characters
[:space:] Space characters (nonprinting), such as carriage return, newline, vertical tab, and form feed
[:upper:] Uppercase alphabetic characters
[:xdigit:] Hexidecimal characters

Quantifier Characters
Character Class 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
\n Cause the previous expression to be repeated n times

Alternative Matching And Grouping Characters
Character Class Description
| Separates alternates, often used with grouping operator ()
( ) Groups subexpression into a unit for alternations, for quantifiers, or for backreferencing (see "Backreferences" section)
[char] Indicates a character list; most metacharacters inside a character list are understood as literals, with the exception of character classes, and the ^ and - metacharacters

Demo Table
CREATE TABLE test (
testcol VARCHAR2(50));

INSERT INTO test VALUES ('abcde');
INSERT INTO test VALUES ('12345');
INSERT INTO test VALUES ('1a4A5');
INSERT INTO test VALUES ('12a45');
INSERT INTO test VALUES ('12aBC');
INSERT INTO test VALUES ('12abc');
INSERT INTO test VALUES ('12ab5');
INSERT INTO test VALUES ('12aa5');
INSERT INTO test VALUES ('12AB5');
INSERT INTO test VALUES ('ABCDE');
INSERT INTO test VALUES ('123-5');
INSERT INTO test VALUES ('12.45');
INSERT INTO test VALUES ('1a4b5');
INSERT INTO test VALUES ('1 3 5');
INSERT INTO test VALUES ('1  45');
INSERT INTO test VALUES ('1   5');
INSERT INTO test VALUES ('a  b  c  d');
INSERT INTO test VALUES ('a b  c   d    e');
INSERT INTO test VALUES ('a              e');
INSERT INTO test VALUES ('Steven');
INSERT INTO test VALUES ('Stephen');
INSERT INTO test VALUES ('111.222.3333');
INSERT INTO test VALUES ('222.333.4444');
INSERT INTO test VALUES ('333.444.5555');
INSERT INTO test VALUES ('abcdefabcdefabcxyz');
COMMIT;
 
REGEXP_COUNT
Syntax REGEXP_COUNT(<source_string>, <pattern>[[, <start_position>], [<match_parameter>]])

-- match parameter:
'c' = case sensitive
'i' = case insensitive search
'm' = treats the source string as multiple lines
'n' = allows the period (.) wild character to match newline
'x' = ignore whitespace characters

Count's occurrences based on a regular expression
SELECT REGEXP_COUNT(testcol, '2a', 1, 'i') RESULT
FROM test;

SELECT REGEXP_COUNT(testcol, 'e', 1, 'i') RESULT
FROM test;
 
REGEXP_INSTR
Syntax REGEXP_INSTR(<source_string>, <pattern>[[, <start_position>][, <occurrence>][, <return_option>][, <match_parameter>][, <sub_expression>]])

Find character 'o' followed by any 3 alphabetic characters: case insensitive

Our thanks to Cassio for spotting a typo here.

SELECT REGEXP_INSTR('500 Oracle Pkwy, Redwood Shores, CA', '[o][[:alpha:]]{3}', 1, 1, 0, 'i') RESULT
FROM DUAL;

SELECT REGEXP_INSTR('500 Oracle Pkwy, Redwood Shores, CA', '[o][[:alpha:]]{3}', 1, 1, 1, 'i') RESULT
FROM DUAL;

SELECT REGEXP_INSTR('500 Oracle Pkwy, Redwood Shores, CA', '[o][[:alpha:]]{3}', 1, 2, 0, 'i') RESULT
FROM DUAL;

SELECT REGEXP_INSTR('500 Oracle Pkwy, Redwood Shores, CA', '[o][[:alpha:]]{3}', 1, 2, 1, 'i') RESULT
FROM DUAL;
Find the position of try, trying, tried or tries SELECT REGEXP_INSTR('We are trying to make the subject easier.', 'tr(y(ing)?|(ied)|(ies))') RESULTNUM
FROM DUAL;
Using Sub-Expression option SELECT testcol, REGEXP_INSTR(testcol, 'ab', 1, 1, 0, 'i', 0)
FROM test;

SELECT testcol, REGEXP_INSTR(testcol, 'ab', 1, 1, 0, 'i', 1)
FROM test;

SELECT testcol, REGEXP_INSTR(testcol, 'a(b)', 1, 1, 0, 'i', 1)
FROM test;
 
REGEXP_LIKE
Syntax REGEXP_LIKE(<source_string>, <pattern>, <match_parameter>)

AlphaNumeric Characters
SELECT *
FROM test
WHERE REGEXP_LIKE(testcol, '[[:alnum:]]');

SELECT *
FROM test
WHERE REGEXP_LIKE(testcol, '[[:alnum:]]{3}');

SELECT *
FROM test
WHERE REGEXP_LIKE(testcol, '[[:alnum:]]{5}');

Alphabetic Characters
SELECT *
FROM test
WHERE REGEXP_LIKE(testcol, '[[:alpha:]]');

SELECT *
FROM test
WHERE REGEXP_LIKE(testcol, '[[:alpha:]]{3}');

SELECT *
FROM test
WHERE REGEXP_LIKE(testcol, '[[:alpha:]]{5}');

Control Characters
INSERT INTO test VALUES ('zyx' || CHR(13) || 'wvu');
COMMIT;

SELECT *
FROM test
WHERE REGEXP_LIKE(testcol, '[[:cntrl:]]{1}');

Digits
SELECT *
FROM test
WHERE REGEXP_LIKE(testcol, '[[:digit:]]');

SELECT *
FROM test
WHERE REGEXP_LIKE(testcol, '[[:digit:]]{3}');

SELECT *
FROM test
WHERE REGEXP_LIKE(testcol, '[[:digit:]]{5}');

Lower Case
SELECT *
FROM test
WHERE REGEXP_LIKE(testcol, '[[:lower:]]');

SELECT *
FROM test
WHERE REGEXP_LIKE(testcol, '[[:lower:]]{2}');

SELECT *
FROM test
WHERE REGEXP_LIKE(testcol, '[[:lower:]]{3}');

SELECT *
FROM test
WHERE REGEXP_LIKE(testcol, '[[:lower:]]{5}');

Printable Characters
SELECT *
FROM test
WHERE REGEXP_LIKE(testcol, '[[:print:]]{5}');

SELECT *
FROM test
WHERE REGEXP_LIKE(testcol, '[[:print:]]{6}');

SELECT *
FROM test
WHERE REGEXP_LIKE(testcol, '[[:print:]]{7}');

Punctuation
TRUNCATE TABLE test;

SELECT *
FROM test
WHERE REGEXP_LIKE(testcol, '[[:punct:]]');

Spaces
SELECT *
FROM test
WHERE REGEXP_LIKE(testcol, '[[:space:]]');

SELECT *
FROM test
WHERE REGEXP_LIKE(testcol, '[[:space:]]{2}');

SELECT *
FROM test
WHERE REGEXP_LIKE(testcol, '[[:space:]]{3}');

SELECT *
FROM test
WHERE REGEXP_LIKE(testcol, '[[:space:]]{5}');

Upper Case
SELECT *
FROM test
WHERE REGEXP_LIKE(testcol, '[[:upper:]]');

SELECT *
FROM test
WHERE REGEXP_LIKE(testcol, '[[:upper:]]{2}');

SELECT *
FROM test
WHERE REGEXP_LIKE(testcol, '[[:upper:]]{3}');
Values Starting with 'a%b'  SELECT testcol
FROM test
WHERE REGEXP_LIKE(testcol, '^ab*');
'a' is the third value SELECT testcol
FROM test
WHERE REGEXP_LIKE(testcol, '^..a.');
Contains two consecutive occurances of the letter 'a' or 'z' SELECT testcol
FROM test
WHERE REGEXP_LIKE(testcol, '([az])\1', 'i');
Begins with 'Ste' ends with 'en' and contains either 'v' or 'ph' in the center SELECT testcol
FROM test
WHERE REGEXP_LIKE(testcol, '^Ste(v|ph)en$');
Use a regular expression in a check constraint CREATE TABLE mytest (c1 VARCHAR2(20), 
CHECK (REGEXP_LIKE(c1, '^[[:alpha:]]+$')));

Identify SSN

Thanks: Byron Bush HIOUG
CREATE TABLE ssn_test (
ssn_col  VARCHAR2(20));

INSERT INTO ssn_test VALUES ('111-22-3333');
INSERT INTO ssn_test VALUES ('111=22-3333');
INSERT INTO ssn_test VALUES ('111-A2-3333');
INSERT INTO ssn_test VALUES ('111-22-33339');
INSERT INTO ssn_test VALUES ('111-2-23333');
INSERT INTO ssn_test VALUES ('987-65-4321');
COMMIT;

SELECT ssn_col
from ssn_test
WHERE REGEXP_LIKE(ssn_col,'^[0-9]{3}-[0-9]{2}-[0-9]{4}$');
 
REGEXP_REPLACE
Syntax REGEXP_REPLACE(<source_string>, <pattern>,
<replace_string>, <position>, <occurrence>, <match_parameter>)
Looks for the pattern xxx.xxx.xxxx and reformats  pattern to (xxx) xxx-xxxx col testcol format a15
col result format a15

SELECT testcol, REGEXP_REPLACE(testcol,
'([[:digit:]]{3})\.([[:digit:]]{3})\.([[:digit:]]{4})',
'(\1) \2-\3') RESULT
FROM test
WHERE LENGTH(testcol) = 12;
Put a space after every character SELECT testcol, REGEXP_REPLACE(testcol, '(.)', '\1 ') RESULT
FROM test
WHERE testcol like 'S%';
Replace multiple spaces with a single space SELECT REGEXP_REPLACE('500    Oracle    Parkway, Redwood    Shores, CA', '( ){2,}', ' ') RESULT
FROM DUAL;
Insert a space between a lower case character followed by an upper case character SELECT REGEXP_REPLACE('George McGovern', '([[:lower:]])([[:upper:]])', '\1 \2') CITY
FROM DUAL;

(Produces 'George Mc Govern')
Replace the period with a string (note use of '\') SELECT REGEXP_REPLACE('We are trying to make the subject easier.','\.',' for you.') REGEXT_SAMPLE
FROM DUAL;
Demo CREATE TABLE t(
testcol VARCHAR2(10));

INSERT INTO t VALUES ('1');
INSERT INTO t VALUES ('2    ');
INSERT INTO t VALUES ('3 new  ');

col newval format a10

SELECT LENGTH(testcol) len, testcol origval, 
REGEXP_REPLACE(testcol, '\W+$', ' ') newval,
LENGTH(REGEXP_REPLACE(testcol, '\W+$', ' ')) newlen
FROM t;
Code snippet courtesy of Valentin Matak.
This is a handy way to remove duplicate characters from a string. This example shows the 1+ repeatability qualifier in use.
SELECT REGEXP_REPLACE('ABBBCABBCCCAABAAAAA', '(A|B|C)\1+', '\1')
FROM DUAL;
 
REGEXP_SUBSTR
Syntax REGEXP_SUBSTR(source_string, pattern
[, position [, occurrence
[, match_parameter]]])
Searches for a comma followed by one or more occurrences of non-comma characters followed by a comma SELECT REGEXP_SUBSTR('500 Oracle Parkway, Redwood Shores, CA', ',[^,]+,') RESULT
FROM DUAL;
Look for http:// followed by a substring of one or more alphanumeric characters and optionally, a period (.) col result format a50

SELECT REGEXP_SUBSTR('Go to http://www.oracle.com/products and click on database',
'http://([[:alnum:]]+\.?){3,4}/?') RESULT
FROM DUAL;
Extracts try, trying, tried or tries SELECT REGEXP_SUBSTR('We are trying to make the subject easier.','tr(y(ing)?|(ied)|(ies))')
FROM DUAL;
Extract the 3rd field treating ':' as a delimiter SELECT REGEXP_SUBSTR('system/pwd@orabase:1521:sidval',
'[^:]+', 1, 3) RESULT
FROM DUAL;

Extract from string with vertical bar delimiter
CREATE TABLE regexp (
testcol VARCHAR2(50));

INSERT INTO regexp
(testcol)
VALUES
('One|Two|Three|Four|Five');

SELECT * FROM regexp;

SELECT REGEXP_SUBSTR(testcol,'[^|]+', 1, 3)
FROM regexp;
Equivalence classes SELECT REGEXP_SUBSTR('iSelfSchooling NOT ISelfSchooling', '[[=i=]]SelfSchooling') RESULT 
FROM DUAL;

Parsing Demo
set serveroutput on

DECLARE
 x VARCHAR2(2);
 y VARCHAR2(2);
 c VARCHAR2(40) := '1:3,4:6,8:10,3:4,7:6,11:12';
BEGIN
  x := REGEXP_SUBSTR(c,'[^:]+', 1, 1);
  y := REGEXP_SUBSTR(c,'[^,]+', 3, 1);

  dbms_output.put_line(x ||' '|| y);
END;
/
 
Related Topics
Substring-Instring
Translate-Replace
 
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