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
