Comments on: PostgreSQL Check Constraint Supports Regular Expressions

By: jayanth

jayanth — Mon, 16 Jun 2008 11:40:02 +0000

syntax:

ALTER Table Table_name
ADD constraints CHECK_column_name
CHECK (REGEXP_LIKE(column_name,’(([0-9][a-z]{1}|[a-z][0-9]{1}))’));

consider the above syntax whether it is an apporiate syntax to create an constraint for a particular column

Example:
ALTER Table userinfo
ADD constraints CHECK_password
CHECK (REGEXP_LIKE(password,’(([0-9][a-z]{1}|[a-z][0-9]{1}))’));

unable to determine the fault ,since the query is unable to get updated..
Kindly reply at your earliest.

Regards
Jayanth S.

By: Preston

Preston — Sat, 16 Sep 2006 21:18:13 +0000

Hi Peter,

If the purpose of this check is to only allow lowercase letters (as it is stated in the description), then what we want is a case sensitive search. With the star, the check will allow both uppercase and lowercase letters.

By: Peter

Peter — Mon, 11 Sep 2006 11:52:04 +0000

No Preston, The star means the expression is case insensitive.

By: Rhyll > PostgreSQL Blog > Using Regular Expressions in PostgreSQL

Rhyll > PostgreSQL Blog > Using Regular Expressions in PostgreSQL — Mon, 06 Feb 2006 19:40:36 +0000

[...] One a related note, I wrote a simple example on using regular expressions in check constraints. [...]

By: Todd Huss’ blog » Blog Archive » More powerful database constraints with regular expressions

Thu, 26 Jan 2006 17:01:44 +0000

[...] Postgres is one of the few databases I’m aware of that currently solves the problem. You can see an example at Joseph Scott’s Blog of using a regex in a check constraint. [...]

By: Preston

Preston — Mon, 20 Jun 2005 04:49:27 +0000

Thanks for the example! One small correction, I think your last line should read:

( first_name ~ ‘^[a-z]+$’)

By: Neil Conway

Neil Conway — Mon, 12 Jul 2004 10:16:04 +0000

Jeff: Yeah, 7.4+ uses an import of the regex code in recent versions of TCL. That code is itself a new version of Henry Spencer’s regex code (updated by none other than Henry Spencer himself); it is not pcre, though. Nevertheless, PostgreSQL’s regex implementation is pretty featureful.

By: Jeff Eckermann

Jeff Eckermann — Wed, 26 May 2004 14:30:08 +0000

As of version 7.4, the regular expression engine used by PostgreSQL is the same as that used by tcl (the language, that is). I haven’t investigated it’s capabilities yet, but I am given to understand that it supports a lot of Perl-style regex extensions. Whether it is “PCRE”, I can’t say.