Thread: using LIMIT only on primary table

If I want the last 100 orders:

SELECT * FROM orders LIMIT 100;

If I want all the items on the last 100 orders, I'd start like this:

SELECT * 
from orders, order_items 
where order_items.order_id = orders.id
LIMIT 100

But that will only give me the last 100 items, not 100 orders.

What I really want is 

SELECT * 
from orders, order_items 
where order_items.order_id = orders.id
and exists
(SELECT * from orders order by ID DESC limit 100);

But that gives me all orders, not just the first 100.

Adding a LIMIT 100 to the above doesn't work either.  It equates to the 
first example.

Clues?  cheers
-- 
Dan Langille
The FreeBSD Diary - http://freebsddiary.org/ - practical examples

"Dan Langille" <dan@langille.org> writes:
> If I want all the items on the last 100 orders, I'd start like this:

> SELECT * 
> from orders, order_items 
> where order_items.order_id = orders.id
> LIMIT 100

I think you want

SELECT * 
from (SELECT * from orders order by ID DESC limit 100) as recent_orders, order_items 
where order_items.order_id = recent_orders.id
        regards, tom lane

On 2 Mar 2002 at 18:22, Tom Lane wrote:

> "Dan Langille" <dan@langille.org> writes:
> > If I want all the items on the last 100 orders, I'd start like this:
> 
> > SELECT * 
> > from orders, order_items 
> > where order_items.order_id = orders.id
> > LIMIT 100
> 
> I think you want
> 
> SELECT * 
> from
>   (SELECT * from orders order by ID DESC limit 100) as recent_orders,
>   order_items 
> where order_items.order_id = recent_orders.id

That is it Tom.  Thank you.  As soon as I saw your solution, I thought of 
creating a view to do this.
  CREATE VIEW recent orders AS   SELECT * from orders   order by ID DESC   limit 100;

Which makes the query:
  SELECT *   from recent_orders, order_items   where order_items.order_id = recent_orders.id

Cheers
-- 
Dan Langille
The FreeBSD Diary - http://freebsddiary.org/ - practical examples

On Sat, 2 Mar 2002 17:35:31 -0500
"Dan Langille" <dan@langille.org> wrote:

> If I want the last 100 orders:
> 
> SELECT * FROM orders LIMIT 100;
> 
> If I want all the items on the last 100 orders, I'd start like this:
> 
> SELECT * 
> from orders, order_items 
> where order_items.order_id = orders.id
> LIMIT 100
> 
> But that will only give me the last 100 items, not 100 orders.
> 
> What I really want is 
> 
> SELECT * 
> from orders, order_items 
> where order_items.order_id = orders.id
> and exists
> (SELECT * from orders order by ID DESC limit 100);


This probably gives you all the items on the last 100 orders.
select *  from (select * from orders order by ID desc limit 10) as o      inner join order_items as oi       on
(oi.order_id= o.order_id)
 
;


> 
> But that gives me all orders, not just the first 100.
> 
> Adding a LIMIT 100 to the above doesn't work either.  It equates to the 
> first example.



Regards,
Masaru Sugawara