Re: stupid select question...

NOT IN will not work if u have nulls in the list.
Anand
On Sun, Jan 14, 2001 at 01:25:59PM +0000, Oliver Elphick wrote:
>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
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>     "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
>