![LIKE operator
% matches zero or more of any character
_ matches exactly one character
Examples
WHERE col1 LIKE 'abc%';
WHERE col1 LIKE '%abc';
WHERE col1 LIKE 'ab_d';
WHERE col1 LIKE 'ab_d' escape '';
WHERE col1 NOT LIKE 'abc%';
Very limited functionality
Check whether first character is numeric: where c1 like '0%' OR c1
like '1%' OR .. .. c1 like '9%'
Very trivial with Regular Exp: where regexp_like(c1, '^[0-9]')](https://image.slidesharecdn.com/regularexpressionsinoracle-120508161259-phpapp02/85/Regular-expressions-in-oracle-6-320.jpg)
![Regular Expressions
Meta Meaning
character
. Matches any single "character" except newline.
* Matches zero or more of the character preceding it
e.g.: bugs*, table.*
^ Denotes the beginning of the line. ^A denotes lines starting
with A
$ Denotes the end of the line. :$ denotes lines ending with :
Escape character (., *, [, , etc)
[] matches one or more characters within the brackets. e.g.
[aeiou], [a-z], [a-zA-Z], [0-9], [:alpha:], [a-z?,!]
[^] negation - matches any characters other than the ones
inside brackets. eg. ^[^13579] denotes all lines not starting
with odd numbers, [^02468]$ denotes all lines not ending
with even numbers
7](https://image.slidesharecdn.com/regularexpressionsinoracle-120508161259-phpapp02/85/Regular-expressions-in-oracle-7-320.jpg)
![POSIX Character Classes
POSIX Description
[:alnum:] Alphanumeric characters
[:alpha:] Alphabetic characters
[:ascii:] ASCII characters
[:blank:] Space and tab
[:cntrl:] Control characters
[:digit:] Digits, Hexadecimal digits
[:xdigit:]
[:graph:] Visible characters (i.e. anything except spaces, control characters,
etc.)
[:lower:] Lowercase letters
[:print:] Visible characters and spaces (i.e. anything except control
characters)
[:punct:] Punctuation and symbols.
[:space:] All whitespace characters, including line breaks
[:upper:] Uppercase letters
[:word:] Word characters (letters, numbers and underscores)](https://image.slidesharecdn.com/regularexpressionsinoracle-120508161259-phpapp02/85/Regular-expressions-in-oracle-9-320.jpg)
![Perl Character Classes
Perl POSIX Description
d [[:digit:]] [0-9]
D [^[:digit:]] [^0-9]
w [[:alnum:]_] [0-9a-zA-Z_]
W [^[:alnum:]_] [^0-9a-zA-Z_]
s [[:space:]]
S [^[:space:]]
10](https://image.slidesharecdn.com/regularexpressionsinoracle-120508161259-phpapp02/85/Regular-expressions-in-oracle-10-320.jpg)
![REGEXP_LIKE
Determines whether pattern matches.
REGEXP_LIKE (source_str, pattern,
[,match_parameter])
Returns TRUE or FALSE.
Use in WHERE clause to return rows matching a pattern
Use as a constraint
alter table t add constraint alphanum check (regexp_like (x,
'[[:alnum:]]'));
Use in PL/SQL to return a boolean.
IF (REGEXP_LIKE(v_name, '[[:alnum:]]')) THEN ..
Can't be used in SELECT clause
regexp_like.sql](https://image.slidesharecdn.com/regularexpressionsinoracle-120508161259-phpapp02/85/Regular-expressions-in-oracle-13-320.jpg)
![REGEXP_SUBSTR
Extracts the matching pattern. Returns NULL when
nothing matches
REGEXP_SUBSTR(source_str, pattern [, position
[, occurrence [, match_parameter]]])
position: character at which to begin the search.
Default is 1
occurrence: The occurrence of pattern you want to
extract
regexp_substr.sql](https://image.slidesharecdn.com/regularexpressionsinoracle-120508161259-phpapp02/85/Regular-expressions-in-oracle-14-320.jpg)
![REGEXP_INSTR
Returns the location of match in a string
REGEXP_INSTR(source_str, pattern, [, position [,
occurrence [, return_option [, match_parameter]]]])
return_option:
0, the default, returns the position of the first character.
1 returns the position of the character following the occurence.
regexp_instr.sql](https://image.slidesharecdn.com/regularexpressionsinoracle-120508161259-phpapp02/85/Regular-expressions-in-oracle-15-320.jpg)
![REGEXP_REPLACE
Search and Replace a pattern
REGEXP_REPLACE(source_str, pattern
[, replace_str] [, position [, occurrence
[, match_parameter]]]])
If replace_str is not specified, pattern/search_str is
replaced with empty string
occurence:
when 0, the default, replaces all occurrences of the match.
when n, any positive integer, replaces the nth occurrence.
regexp_replace.sql](https://image.slidesharecdn.com/regularexpressionsinoracle-120508161259-phpapp02/85/Regular-expressions-in-oracle-16-320.jpg)
![REGEXP_COUNT
New in 11g
Returns the number of times a pattern appears in a
string.
REGEXP_COUNT(source_str, pattern [,position
[,match_param]])
For simple patterns it is same as
(LENGTH(source_str) –
LENGTH(REPLACE(source_str,
pattern)))/LENGTH(pattern)
regexp_count.sql](https://image.slidesharecdn.com/regularexpressionsinoracle-120508161259-phpapp02/85/Regular-expressions-in-oracle-17-320.jpg)
![A few other points
When not to use Regular Expressions
If the same thing could be used without regular
expressions and without too much coding.
POSIX notations need double brackets [[:upper]]. [:upper:]
won't work. [[:UPPER:]] won't work either. It has to be in
lower case letters.
Locale support provided with Collation Element ][.ce.]],
and Equivalence Classes [[=e=]]
MySQL supports regular expressions with RLIKE](https://image.slidesharecdn.com/regularexpressionsinoracle-120508161259-phpapp02/85/Regular-expressions-in-oracle-34-320.jpg)
Regular expressions in oracle
- 1. Regular Expressions in Oracle Logan Palanisamy
- 2. Agenda Introduction to regular expressions REGEXP_* functions in Oracle Coffee Break Examples More examples
- 3. Meeting Basics Put your phones/pagers on vibrate/mute Messenger: Change the status to offline or in-meeting Remote attendees: Mute yourself (*6). Ask questions via Adobe Connect.
- 4. What are Regular Expressions? A way to express patterns credit cards, license plate numbers, vehicle identification numbers, voter id, driving license UNIX (grep, egrep), PHP, JAVA support Regular Expressions PERL made it popular
- 5. String operations before Regular Expression support in Oracle Pull the data from DB and perform it in middle tier or FE OWA_PATTERN in 9i and before LIKE operator
- 6. LIKE operator % matches zero or more of any character _ matches exactly one character Examples WHERE col1 LIKE 'abc%'; WHERE col1 LIKE '%abc'; WHERE col1 LIKE 'ab_d'; WHERE col1 LIKE 'ab_d' escape ''; WHERE col1 NOT LIKE 'abc%'; Very limited functionality Check whether first character is numeric: where c1 like '0%' OR c1 like '1%' OR .. .. c1 like '9%' Very trivial with Regular Exp: where regexp_like(c1, '^[0-9]')
- 7. Regular Expressions Meta Meaning character . Matches any single "character" except newline. * Matches zero or more of the character preceding it e.g.: bugs*, table.* ^ Denotes the beginning of the line. ^A denotes lines starting with A $ Denotes the end of the line. :$ denotes lines ending with : Escape character (., *, [, , etc) [] matches one or more characters within the brackets. e.g. [aeiou], [a-z], [a-zA-Z], [0-9], [:alpha:], [a-z?,!] [^] negation - matches any characters other than the ones inside brackets. eg. ^[^13579] denotes all lines not starting with odd numbers, [^02468]$ denotes all lines not ending with even numbers 7
- 8. Extended Regular Expressions Meta character Meaning | alternation. e.g.: ho(use|me), the(y|m), (they|them) + one or more occurrences of previous character. ? zero or one occurrences of previous character. {n} exactly n repetitions of the previous char or group {n,} n or more repetitions of the previous char or group {,m} zero to m repetitions of the previous char or group {n, m} n to m repetitions of previous char or group (....) grouping or subexpression n back referencing where n stands for the nth sub- expression. e.g.: 1 is the back reference for first sub-expression. 8
- 9. POSIX Character Classes POSIX Description [:alnum:] Alphanumeric characters [:alpha:] Alphabetic characters [:ascii:] ASCII characters [:blank:] Space and tab [:cntrl:] Control characters [:digit:] Digits, Hexadecimal digits [:xdigit:] [:graph:] Visible characters (i.e. anything except spaces, control characters, etc.) [:lower:] Lowercase letters [:print:] Visible characters and spaces (i.e. anything except control characters) [:punct:] Punctuation and symbols. [:space:] All whitespace characters, including line breaks [:upper:] Uppercase letters [:word:] Word characters (letters, numbers and underscores)
- 10. Perl Character Classes Perl POSIX Description d [[:digit:]] [0-9] D [^[:digit:]] [^0-9] w [[:alnum:]_] [0-9a-zA-Z_] W [^[:alnum:]_] [^0-9a-zA-Z_] s [[:space:]] S [^[:space:]] 10
- 11. Tools to learn Regular Expressions http://www.weitz.de/regex-coach/ http://www.regexbuddy.com/
- 12. REGEXP_* functions Available from 10g onwards. Powerful and flexible, but CPU-hungry. Easy and elegant, but sometimes less performant Usable on text literal, bind variable, or any column that holds character data such as CHAR, NCHAR, CLOB, NCLOB, NVARCHAR2, and VARCHAR2 (but not LONG). Useful as column constraint for data validation
- 13. REGEXP_LIKE Determines whether pattern matches. REGEXP_LIKE (source_str, pattern, [,match_parameter]) Returns TRUE or FALSE. Use in WHERE clause to return rows matching a pattern Use as a constraint alter table t add constraint alphanum check (regexp_like (x, '[[:alnum:]]')); Use in PL/SQL to return a boolean. IF (REGEXP_LIKE(v_name, '[[:alnum:]]')) THEN .. Can't be used in SELECT clause regexp_like.sql
- 14. REGEXP_SUBSTR Extracts the matching pattern. Returns NULL when nothing matches REGEXP_SUBSTR(source_str, pattern [, position [, occurrence [, match_parameter]]]) position: character at which to begin the search. Default is 1 occurrence: The occurrence of pattern you want to extract regexp_substr.sql
- 15. REGEXP_INSTR Returns the location of match in a string REGEXP_INSTR(source_str, pattern, [, position [, occurrence [, return_option [, match_parameter]]]]) return_option: 0, the default, returns the position of the first character. 1 returns the position of the character following the occurence. regexp_instr.sql
- 16. REGEXP_REPLACE Search and Replace a pattern REGEXP_REPLACE(source_str, pattern [, replace_str] [, position [, occurrence [, match_parameter]]]]) If replace_str is not specified, pattern/search_str is replaced with empty string occurence: when 0, the default, replaces all occurrences of the match. when n, any positive integer, replaces the nth occurrence. regexp_replace.sql
- 17. REGEXP_COUNT New in 11g Returns the number of times a pattern appears in a string. REGEXP_COUNT(source_str, pattern [,position [,match_param]]) For simple patterns it is same as (LENGTH(source_str) – LENGTH(REPLACE(source_str, pattern)))/LENGTH(pattern) regexp_count.sql
- 18. Pattern Matching modifiers i – Specifies case-insensitive matching (ignore case) c – Specifies case-sensitive matching n – allows the period (.) to match the newline character m - treats the source string as multiple lines. x - ignores whitespace characters when match_parameter is not specified, case sensitivity is determined by NLS_SORT parameter (BINARY, BINARY_CI) A period (.) doesn't match newline character Source string is treated as a single line match_params.sql
- 19. Is a CHAR column all numeric? to_number(c1) returns ORA-01722: invalid number if a varchar2 column contains alpha characters. is_numeric.sql
- 20. Check constraints Put validation close to where the data is stored No need to have validation at different clients check_constraint.sql
- 21. Extract email-ids Find email-ids embedded in text strings. Possible email-id formats: [email protected] [email protected] [email protected] extract_emailid.sql
- 22. Extract dates Extract dates embedded in text strings. Possible formats 1/5/2007, 2-5-03, 12-31-2009, 1/31/10, 2/5-10 extract_date.sql
- 23. Extracting hostnames from URLs Extract hostnames/domain-names embedded in text strings. Possible formats http://us.mg201.mail.yahoo.com/dc/launch?.partner =sbc&.gx=1&.rand=fegr2vucbecu5 https://www.mybank.com:8080/abc/xyz www.mybank.com ftp://www.mycharity.org/abc/xyz extract_hostname.sql
- 24. Convert value pairs to XML Input: A string such as 'remain1=1;remain2=2;' Output: An XML string <remain1><value=1></remain1> <remain2><value=2></remain2> convert_to_xml.sql
- 25. Sort IP addresses in numerical order Sort IP addresses, that are stored as character strings, in numerical order. Input 10.10.20.10 127.0.0.1 166.22.33.44 187.222.121.0 20.23.23.20 sort_ip_address.sql
- 26. Extract first name, last name, and middle initial Extract the first name, last name with an optional middle initial. first_last_mi.sql
- 27. Finding the Last Occurrence Find the last numeric sequence from a sequence. Return 567 from 'abc/123/def567/xyz' INSTR and SUBSTR allow backward search when position is negative. REGEXP functions don't allow backward search last_occurrence.sql
- 28. Fuzzy Match Tables t1 and t2 each have a varchar2(12) column (t1.x, t2.y). A row in t1 is considered a match for a row in t2, if any six characters in t1.x matches with any six characters in t2.y fuzzy_match.sql
- 29. The lazy operator ? is lazy/non-greedy quantifier greedy_lazy.sql
- 30. Meta-characters with multiple meanings Same meta characters are used with multiple meanings ^ used for anchoring and negation. ? used as quantifier and lazy operator () used for grouping or sub-expression metachars_with_multiple_meanings.sql
- 31. Nuances ? (zero or one), * (zero or more) could sometimes mislead you nuances.sql
- 32. Stored patterns patterns can be stored in table columns and be referenced in REGEXP functions No need to hard-code them stored_patterns.sql
- 33. Random things Insert a dash before the two last digits Remove a substring Get rid of useless commas from a string Find the word that comes immediately before a substring (e.g. XXX) Replace whole words, not its parts Trimming the trailing digits random.sql
- 34. A few other points When not to use Regular Expressions If the same thing could be used without regular expressions and without too much coding. POSIX notations need double brackets [[:upper]]. [:upper:] won't work. [[:UPPER:]] won't work either. It has to be in lower case letters. Locale support provided with Collation Element ][.ce.]], and Equivalence Classes [[=e=]] MySQL supports regular expressions with RLIKE
- 35. References Oracle® Database Advanced Application Developer's Guide (http://download.oracle.com/docs/cd/E11882_0 1/appdev.112/e17125/adfns_regexp.htm#CHDGH BHF) Anti-Patterns in Regular Expressions: http://gennick.com/antiregex.html First Expressions. An article by Jonathan Gennick Oracle Magazine, Sep/Oct 2003. Oracle Regular Expressions Pocket Reference by Gonathan Gennick http://examples.oreilly.com/9780596006013/Re gexPocketData.sql
- 36. References ... http://www.psoug.org/reference/regexp.html http://download.oracle.com/docs/cd/E11882_01/se rver.112/e10592/conditions007.htm#SQLRF00501 http://www.oracle.com/technology/pub/articles/sat ernos_regexp.html http://www.oracle.com/technology/products/datab ase/application_development/pdf/TWP_Regular_E xpressions.pdf http://asktom.oracle.com/pls/asktom/asktom.searc h?p_string=regexp_
- 37. References ... http://www.oracle.com/technology/obe/10gr2_db_single/de velop/regexp/regexp_otn.htm http://www.oracle.com/technology/sample_code/tech/pl_sq l/index.html http://forums.oracle.com/forums/thread.jspa?threadID=427 716 http://forums.oracle.com/forums/search.jspa?threadID=&q= regular+expression&objID=f75&dateRange=all&userID=&nu mResults=120&rankBy=9 http://www.oracle.com/technology/sample_code/tech/pl_sq l/index.html http://asktom.oracle.com/pls/apex/f?p=100:11:0::::P11_QUE STION_ID:2200894550208#1568589800346862515