Re: 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

Try this:

SELECT *
from order_items
where order_id in (select ID from orders order by ID desc limit 100);

DAQ

"Dan Langille" <dan(at)langille(dot)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(at)langille(dot)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(at)langille(dot)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