From: Gary Stainburn <gary.stainburn@ringways.co.uk>
Organization: Ringways Garages Ltd
To: pgsql-sql@postgresql.org
Subject: simple "select / if found" isn't
Date: Fri, 16 Dec 2016 11:02:37 +0000
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I'm creating a simple function that must have been done millions of times 
before, but I can't get it to work.  In this case, I'm checking a user ID and 
password against previously used passwords:

All I want to do is return 'found' based on the select but I can't get it to 
work.  

If I run 

select 1 from user_previous_passwords 
	where u_id=25 and 
	crypt('MyPaSSword',u_previous_password) = u_previous_password;

then it returns the matching row(s)

If I run my function

create or replace function check_previous_passwords (ID int4, PASS varchar) 
returns boolean as $$
DECLARE
  UID int4;
BEGIN
  return exists(select 1 from user_previous_passwords 
    where u_id=ID and crypt(PASS,u_previous_password) = PASS);
END;
$$ LANGUAGE plpgsql;

I always get false;

I've tried things like 

if exist(....) then ....
select 1 into UID
select count(u_id) into UID

update .....set u_id=u_id ......
if found then

but I never get the correct result, so I think I must me doing something much 
more fundamentally wrong.

Can someone spot it please?

Gary


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