Regular Expressions in SQL

What?
Practice makes perfect. Or in my case, any practice is a start. This article serves as a quick note on how to use regular expressions within SQL statements:

How?
For the following examples, I am pretending to select rows from a table called `STUDENTS`.

Oracle PL/SQL
Looking for abnormal data, note the circumflex to exclude the clean alphanumeric rows:
copyraw
SELECT * FROM STUDENTS WHERE REGEXP_LIKE(S_SURNAME, '[^a-zA-Z0-9]')
-- returns all rows where the student surname contains non-alphanumeric characters
-- eg.  O'Brien will be returned

SELECT * FROM STUDENTS WHERE REGEXP_LIKE(S_SURNAME, '[^a-zA-Z0-9\'']')
-- returns all rows where the student surname contains non-alphanumeric characters and does not contain apostrophes
-- eg.  O'Brien will NOT be returned

-- Other REGEXP Functions for Oracle:
-- -- REGEXP_REPLACE(country_name, '(.)', '\1 ')
-- -- REGEXP_INSTR(email, '\w+@\w+(\.\w+)+') > 0
-- -- REGEXP_SUBSTR('oracle', 'o r a c l e', 1, 1, 'x')
  1.  SELECT * FROM STUDENTS WHERE REGEXP_LIKE(S_SURNAME, '[^a-zA-Z0-9]') 
  2.  -- returns all rows where the student surname contains non-alphanumeric characters 
  3.  -- eg.  O'Brien will be returned 
  4.   
  5.  SELECT * FROM STUDENTS WHERE REGEXP_LIKE(S_SURNAME, '[^a-zA-Z0-9\'']') 
  6.  -- returns all rows where the student surname contains non-alphanumeric characters and does not contain apostrophes 
  7.  -- eg.  O'Brien will NOT be returned 
  8.   
  9.  -- Other REGEXP Functions for Oracle: 
  10.  -- -- REGEXP_REPLACE(country_name, '(.)', '\1 ') 
  11.  -- -- REGEXP_INSTR(email, '\w+@\w+(\.\w+)+') > 0 
  12.  -- -- REGEXP_SUBSTR('oracle', 'o r a c l e', 1, 1, 'x') 


Microsoft T-SQL
Note the circumflex/hat to negate the expression in the first example, and then the use of NOT LIKE in the second example:
copyraw
SELECT * FROM [STUDENTS] WHERE [S_SURNAME] LIKE '%[^a-zA-Z0-9]%'
-- returns all rows where the student surname contains non-alphanumeric characters
-- eg.  O'Brien will be returned

SELECT * FROM [STUDENTS] WHERE [S_SURNAME] NOT LIKE '%[a-zA-Z0-9]%'
-- returns all rows where the student surname does NOT contain a letter or number
-- eg.  O'Brien will NOT be returned as it contains letters
  1.  SELECT * FROM [STUDENTS] WHERE [S_SURNAME] LIKE '%[^a-zA-Z0-9]%' 
  2.  -- returns all rows where the student surname contains non-alphanumeric characters 
  3.  -- eg.  O'Brien will be returned 
  4.   
  5.  SELECT * FROM [STUDENTS] WHERE [S_SURNAME] NOT LIKE '%[a-zA-Z0-9]%' 
  6.  -- returns all rows where the student surname does NOT contain a letter or number 
  7.  -- eg.  O'Brien will NOT be returned as it contains letters 


MySQL
And my favorite. Note the circumflex as we are still excluding non-alphanumeric rows.
copyraw
SELECT * FROM Students WHERE studentSurname REGEXP '[^a-zA-Z0-9]';  

or 

SELECT * FROM Students WHERE studentSurname RLIKE '[^a-zA-Z0-9]';

-- returns all rows where the student surname contains non-alphanumeric characters
-- eg.  O'Brien will be returned
  1.  SELECT * FROM Students WHERE studentSurname REGEXP '[^a-zA-Z0-9]'
  2.   
  3.  or 
  4.   
  5.  SELECT * FROM Students WHERE studentSurname RLIKE '[^a-zA-Z0-9]'
  6.   
  7.  -- returns all rows where the student surname contains non-alphanumeric characters 
  8.  -- eg.  O'Brien will be returned 

Category: Databases :: Article: 545

Credit where Credit is Due:


Feel free to copy, redistribute and share this information. All that we ask is that you attribute credit and possibly even a link back to this website as it really helps in our search engine rankings.

Disclaimer: Please note that the information provided on this website is intended for informational purposes only and does not represent a warranty. The opinions expressed are those of the author only. We recommend testing any solutions in a development environment before implementing them in production. The articles are based on our good faith efforts and were current at the time of writing, reflecting our practical experience in a commercial setting.

Thank you for visiting and, as always, we hope this website was of some use to you!

Kind Regards,

Joel Lipman
www.joellipman.com

Related Articles

Joes Revolver Map

Accreditation

Badge - Certified Zoho Creator Associate
Badge - Certified Zoho Creator Associate

Donate & Support

If you like my content, and would like to support this sharing site, feel free to donate using a method below:

Paypal:
Donate to Joel Lipman via PayPal

Bitcoin:
Donate to Joel Lipman with Bitcoin bc1qf6elrdxc968h0k673l2djc9wrpazhqtxw8qqp4

Ethereum:
Donate to Joel Lipman with Ethereum 0xb038962F3809b425D661EF5D22294Cf45E02FebF
© 2024 Joel Lipman .com. All Rights Reserved.