Hi, maybe the subject of this message is not very good. Here is my
problem. Considering a single table, we have a look at two columns. Both
are ID's like that: "post with ID = x belongs to category with ID = y".
I want to perform the following request:
All posts belonging to category 12 are needed; if in this very same
table the same post also belongs to another category, get the ID of that
other category; if the post doesn't belong to any other category, get 0
instead.
For instance, if post with ID 115 belongs to category 12 only,
return (115,0); if on the other hand it belongs to category 12 and 13,
return (115,13).

Thank you by advance, regards, K.

On 12 Oct, 12:20, "K." <k...@somewhere.org> wrote:
> Hi, maybe the subject of this message is not very good. Here is my
> problem. Considering a single table, we have a look at two columns. Both
> are ID's like that: "post with ID = x belongs to category with ID = y".
> I want to perform the following request:
> All posts belonging to category 12 are needed; if in this very same
> table the same post also belongs to another category, get the ID of that
> other category; if the post doesn't belong to any other category, get 0
> instead.
> For instance, if post with ID 115 belongs to category 12 only,
> return (115,0); if on the other hand it belongs to category 12 and 13,
> return (115,13).
>
> Thank you by advance, regards, K.

Suppose it belogs to 12, 13 and 14?

Le Fri, 12 Oct 2007 11:29:05 +0000, Captain Paralytic a écrit:
> Suppose it belogs to 12, 13 and 14?
Sorry for that ; it can't happen in my database (according to what it
really means). But just take any of 13 or 14; it will be OK.

On 12 Oct, 14:51, "K." <k...@somewhere.org> wrote:
> Le Fri, 12 Oct 2007 11:29:05 +0000, Captain Paralytic a écrit:> Supposeit belogs to 12, 13 and 14?
>
> Sorry for that ; it can't happen in my database (according to what it
> really means). But just take any of 13 or 14; it will be OK.

So we'd be looking at something like:

SELECT
CONCAT(
'('
t1.post,
',' ,
IFNULL(t2.category,0),
')'
) `return`
FROM table t1
LEFT JOIN table t2 ON t1.post = t2.post AND t1.category <> t2.category
WHERE t1.category = 12

Le Fri, 12 Oct 2007 15:14:29 +0000, Captain Paralytic a écrit:
> So we'd be looking at something like:

Thank you for everything; I will have a look at that tonight.
Regards, K.