Return next value in Sybase based on condition - sql

Question

I have a table like this:
date ticker price
01/01/17 APPL 700
01/01/17 SNAP 15
01/02/17 APPL 750
01/02/17 SNAP 13
I'd want to retrieve the next price for that ticker as an additional column, like so:
date ticker price next_price
01/01/17 APPL 700 750
01/01/17 SNAP 15 13
01/02/17 APPL 750 NULL
01/02/17 SNAP 13 NULL
I think in most databases you'd be able to do something like this:
SELECT date, ticker, price, RANK() OVER (PARTITION BY ticker
ORDER BY date ASC) AS RANK
from table_name
and then do something with the rank to find the next_price. Unfortunately Sybase ASE is sadly limited and doesn't support RANK().
Any ideas on what to use instead?

Answer 1

Assumptions:
each unique ticker value has a max of 1 record for any given date
next_price is for the next day where 'next' could be defined as +1 day, +2 days, +1 week, +1 month, etc
Off the top of my head ... a bit of a convoluted correlated sub-query to find next_price ...
Setup table and data:
create table mytab
([date] date
,ticker varchar(10)
,price int
)
go
insert mytab values ('1/1/2017','APPL',700)
insert mytab values ('1/1/2017','SNAP',15)
insert mytab values ('1/2/2017','APPL',750)
insert mytab values ('1/2/2017','SNAP',13)
insert mytab values ('1/5/2017','APPL',800)
insert mytab values ('1/7/2017','SNAP',23)
go
One possible query:
select t1.[date],
t1.ticker,
t1.price,
(select price
from mytab t2
where t2.ticker = t1.ticker
and t2.[date] = (-- find the 'next' available day for t1.ticker
select min([date])
from mytab t3
where t3.ticker = t1.ticker
and t3.[date] > t1.[date]
)
) as next_price
from mytab t1
order by 1,2
go
date ticker price next_price
---------------- ---------- ----------- -----------
Jan 1 2017 APPL 700 750
Jan 1 2017 SNAP 15 13
Jan 2 2017 APPL 750 800
Jan 2 2017 SNAP 13 23
Jan 5 2017 APPL 800 NULL
Jan 7 2017 SNAP 23 NULL
Tested on ASE 15.7 SP138

Answer 2

You would not use rank() for this. You would use lead().
You can use a correlated subquery:
select t.*,
(select top 1 t2.price
from table_name t2
where t2.ticker = t.ticker and t2.date > t.date
order by t2.date asc
) as next_price
from table_name t;
If you know the date is the next calendar date, then you could use a left join instead -- that would be more efficient.