if you want topics listed which don't yet have messages try
select
t.id, t.topic,
m.id, m.message from topics t left join messages m on m.topic =
t.id;
On Fri, May 22, 2009 at 8:47 AM, James Kitambara
<jameskitambara@yahoo.co.uk> wrote:
Dear Richard Ekblom,
I think Mr. Adrian Klaver gave you the solution. Mine is the similar solution
After executing this query you will get the following:
id | topic | message
----+----------------------------------+--------------------------
1 | My favorite food | I like lasagna!
2 | My favorite food | Pizza is also a favorite
3 | Are squares better then circles? | I like circles, they
: remind me of pizza
Best Regards, Muhoji James Kitambara Database Administrator, B.Sc. With Computer Science and Statistics (Hons), National Bureau of Statistics, P.O. Box 796, Tel : +255 22 2122722/3 Fax: +255 22 2130852, Mobile : +255 71 3307632, Dar es Salaam, Tanzania.
-----------------------------------------ORGINAL MESSAGE--------------------------------
On Friday 22 May 2009 6:48:43 am Richard Ekblom wrote:
> Hello
>
> I have frequently encountered the need of combining two tables into one.
> First, please take a look at the following table setups...
>
> CREATE TABLE topics (
> id SERIAL PRIMARY KEY,
> topic TEXT NOT NULL
> );
>
> CREATE TABLE messages (
> id SERIAL PRIMARY KEY,
> topic INTEGER REFERENCES topics(id),
> message TEXT NOT NULL
> );
>
> Example of a topics table:
> ID TOPIC
> 1 Are squares better then circles?
> 2 My favorite food
>
> Example of a messages table:
> ID TOPIC MESSAGE
> 1 2 I like lasagna!
> 2 2 Pizza is also a favorite
> 3 1 I like circles, they remind me of pizza
>
> Notice that the number of topics may differ from the number of messages.
>
> Now I want to combine these tables with a single SELECT to get...
>
> Combined table:
> ID TOPIC MESSAGE
> 1 My favorite food I like lasagna!
> 2 My favorite food Pizza is also a favorite
> 3 Are squares better then circles? I like circles, they remind me
> of pizza
>
> I have seen different examples of this with something called JOIN but
> they always give me only two rows. How can I do this when the two tables
> may have different sizes to produce exactly the combined table above???
>
>
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