missing right pharenthesis, subquery error for finding population density

Question

I'm trying to write a query that gets get the population density of which we find by taking the population and dividing it by the area. I have made a subquery

Select max(p.pop)
    from state s
    left join statepop p
    on p.code = s.code
    group by s.name
    Order by max(p.year)

That gets the most recent year, I thought I could take this and drop it into my parent query, and I've tried in two different ways, but I get an error saying "missing right parenthesis." I've read up on things and believe it to be a syntax error but I'm not sure where I'm going wrong. Is there a better way to do this, or can someone point out where in my query it's causing it to throw this error?

select s.name, round( p.population / s.area, 2)
from state s
left join statepop p
on p.code = s.code
where p.pop in (
    Select max(p.pop)
    from state s
    left join statepop p
    on p.code = s.code
    group by s.name
    Order by max(p.year)
)

select s.name, round( (
   Select max(p.pop)
   from state c
   left join statepop p
   on p.code = s.code
   group by s.name
   Order by max(p.year) DESC
   )/ s.area, 2)
from state s
inner join statepop p
on p.code= s.code;

Tables: "state" Code is our key that is unquie for each state

name	code	area
Ohio	OH	50
Wisconsin	WI	100

"statepop"

code	Year	pop
OH	1998	10000
OH	2000	1000
OH	1998	6000
OH	1978	8000
WI	1999	2000
WI	2000	20000
WI	2000	5000

Answer 1

You can use the ROW_NUMBER analytic function so you do not need to query the tables twice:

SELECT name,
       population_density
FROM   (
  SELECT s.name,
         ROUND(p.pop / s.area, 2) AS population_density,
         ROW_NUMBER() OVER (PARTITION BY s.code ORDER BY p.year DESC, p.pop DESC) AS rn
  FROM   state s
         LEFT JOIN statepop p
         ON p.code = s.code
)
WHERE  rn = 1;

If you really did want to use your query then you cannot have an ORDER BY clause in the sub-query within an IN clause. What you probably want is to find the ROWID for the maximum year and population and correlating on the code primary key:

select s.name,
       round( p.pop / s.area, 2)
from   state s
       left join statepop p
       on p.code = s.code
where  p.rowid IN (
         SELECT MAX(ROWID) KEEP (DENSE_RANK LAST ORDER BY year, pop)
         FROM   statepop px
         WHERE  s.code = px.code
       )