Subselect in oracle - oracle

Question

I'm struggling with a subselect in oracle. I want to include the latest price from another table.
Here is my current attempt:
SELECT tab1.*
(select price from
old_prices
where part_no=tab1.article_no
order by valid_from desc) as old_price,
FROM articles tab1
order by article_no
The sub select returns several rows which I think is the problem. But I do not know how to limit the number of rows in Oracle.

Answer 1

SQL> create table articles (article_no,name)
2 as
3 select 1, 'PEN' from dual union all
4 select 2, 'PAPER' from dual
5 /
Table created.
SQL> create table old_prices (part_no,valid_from,price)
2 as
3 select 1, date '2008-01-01', 10 from dual union all
4 select 1, date '2009-01-01', 11 from dual union all
5 select 1, date '2010-01-01', 12 from dual union all
6 select 1, date '2011-01-01', 13 from dual union all
7 select 2, date '2010-01-01', 89.95 from dual union all
8 select 2, date '2011-01-01', 94.95 from dual union all
9 select 2, date '2012-01-01', 99.95 from dual
10 /
Table created.
SQL> select a.article_no
2 , max(a.name) keep (dense_rank last order by p.valid_from) name
3 , max(p.price) keep (dense_rank last order by p.valid_from) price
4 from articles a
5 , old_prices p
6 where a.article_no = p.part_no
7 group by a.article_no
8 /
ARTICLE_NO NAME PRICE
---------- ----- ----------
1 PEN 13
2 PAPER 99.95
2 rows selected.
Regards,
Rob.

Answer 2

If it's the latest price you're after:
SELECT tab1.*, p.price old_price
FROM articles tab1
, old_prices p
where p.part_no = tab1.article_no
and valid_from = (
select MAX(valid_from)
from old_prices p2
where p2.part_no = p.part_no
)
order by article_no

Answer 3

I want to include the lastest price
I presume you mean latest.
OK, well that's a bit of a problem to start with, there are several ways of doing this:
SELECT o.price
FROM old_prices o
WHERE o.part_no=&part_no
AND o.ondate=(SELECT MAX(o2.ondate)
FROM old_prices o2
WHERE o2.part_no=&part_no);
Seems the most obvious choice but its rather innefficient.
You could try....
SELECT ilv.price
FROM (SELECT o.price
FROM old_price o
WHERE o.part_no=&part_no
ORDER BY ondate DESC) ilv
WHERE rownum=1;
Or....
SELECT TO_NUMBER(
SUBSTR(
MAX(TO_CHAR(o.ondate, 'YYYYMMDDHH24MISS') || price)
, 15)
) as latest_price
FROM old_price o
WHERE o.part_no=&part_no;

Answer 4

To limit rows use ROWNUM < 10. This is a pseudocolumn returning the row number of each line of your resultset.
EDIT:
You need to add another subselect query (hope this is the right place for your need)
SELECT tab1.*
select (
(select price from old_prices
where part_no=tab1.article_no order by valid_from desc
) as x
where rownum = 1
) as old_price
FROM articles tab1
order by article_no

Answer 5

SELECT tab1.*
(select
price
from (
SELECT
part_no
, price
, row_number () over (partition by part_no order by valid_from desc ) rn
FROM
old_prices
) P
where rn =1
and tab1.article_no = P.part_no
) as old_price
FROM articles tab1
order by article_no
more efficient would be
SELECT
tab1.*
, P.price
FROM
articles tab1
, ( SELECT
part_no
, price
, row_number () over (partition by part_no order by valid_from desc ) rn
FROM
old_prices
) P
WHERE
P.part_no(+) = tab1.article_no
P.rn(+) = 1
;

Answer 6

with old_prices as(
select level * 15 price ,
mod (level ,5) part_no , --this is just to create a grouping type partno
(sysdate - level ) valid_from
from dual
connect by level < 100)
,
articles as(
select level ,
mod(level , 5 ) article_no ,
(sysdate + level) someOtherDateField
From dual
connect by level < 5
)
SELECT tab1.* ,
old_price.*
from articles tab1
left join
(
select price,
part_no ,
valid_from ,
rank() over(partition by part_no order by valid_from desc) rk
from old_prices
) old_price
on tab1.article_no = old_price.part_no
and old_price.rk = 1
order by article_no ;
Here's another way!
LEVEL ARTICLE_NO SOMEOTHERDATEFIELD PRICE PART_NO VALID_FROM RK
---------------------- ---------------------- ------------------------- ---------------------- ---------------------- ------------------------- ----------------------
1 1 25/05/11 07:30:54 15 1 23/05/11 07:30:54 1
2 2 26/05/11 07:30:54 30 2 22/05/11 07:30:54 1
3 3 27/05/11 07:30:54 45 3 21/05/11 07:30:54 1
4 4 28/05/11 07:30:54 60 4 20/05/11 07:30:54 1