Re: regexp_matches for digit

[Steve Crawford <scrawford@xxxxxxxxxxxxxxxxxxxx>]

Title: Konsole output

On 07/09/2015 09:24 AM, Ramesh T wrote:

Hi,

          in oracle regexp_like(entered date,'[[:digit:]]{4}-[[:digit:]]{2}-[[:digit:]]{2}','i')

for postgres i have regexp_matches ,But i need how to match [:digit:] in postgres when we pass date..?

any help

The tilde operator works fine for me.

select '2014-05-05' ~ '[[:digit:]]{4}-[[:digit:]]{2}-[[:digit:]]{2}';     
?column?  
----------
t

But if you are attempting to validate a date the regex is *way* too simplistic as it will match any manner of junk:
123456-78-901234
thisisan0000-00-00invaliddate
etc.

At a minimum you need to anchor the ends with ^ and $:
'^[[:digit:]]{4}-[[:digit:]]{2}-[[:digit:]]{2}$'


If you can make reasonable assumptions about date ranges you can catch more errors with something like:
'^20[[:digit:]]{2}-[01][[:digit:]]{1}-[0123][[:digit:]]{1}$'

But trying to truly validate dates purely with a regex is more effort than I'm willing to put in. I don't recall where I ran across this snippet but it creates a function that ensures that the date is acceptable to PostgreSQL without raising an error:


CREATE OR REPLACE FUNCTION is_valid_date(text)
   RETURNS bool AS
'
begin
  return case when $1::date is null then false else true end;
exception when others then
  return false;                                               
end;
'
LANGUAGE 'plpgsql' VOLATILE;

Cheers,
Steve