Re: stupid select question...

Konstantinos Agouros wrote:
  >
  >Hi,
  >
  >my sql has gotten a little rusty, here's what I want to do:
  >I have two tables both contain urls. How what I want are all the entries in
  >table b where there is no matching url in table a. I do remember doing somet
      >hing
  >like this with a
  >select url from table1 where a.url not in select url from table b.
  >
  >Can I do this in postgres?

SELECT url FROM a WHERE url NOT IN (select url FROM b);

but watch out for nulls:

bray=# select * from a;
    url
------------
 http:fred1
 http:fred2
(2 rows)

bray=# select * from b;
 id |    url
----+------------
  1 | http:fred1
  2 |                  <-- url is null
(2 rows)

bray=# SELECT url FROM a WHERE url NOT IN (select url FROM b);
 url
-----
(0 rows)

bray=# SELECT url FROM a WHERE url NOT IN (select url FROM b WHERE NOT url IS
NULL);
    url
------------
 http:fred2
(1 row)

--
Oliver Elphick                                Oliver.Elphick@lfix.co.uk
Isle of Wight                              http://www.lfix.co.uk/oliver
PGP: 1024R/32B8FAA1: 97 EA 1D 47 72 3F 28 47  6B 7E 39 CC 56 E4 C1 47
GPG: 1024D/3E1D0C1C: CA12 09E0 E8D5 8870 5839  932A 614D 4C34 3E1D 0C1C
                 ========================================
     "If we confess our sins, he is faithful and just to
      forgive us our sins, and to cleanse us from all
      unrighteousness."          I John 1:9