Question

We have a table that converts SAT scores into ACT scores using a year. if the data changes in the future we would add the new scores along with the year the scores change. We need to pass in a year and sat score and return the correct act score.

sample data with three rows would be

act sat year
28 1010 1998
29 1010 2012
30 1010 2015

If I pass in a SAT score of 1010 and a year of 2014 I should return an act score of 29 back.

I wrote the following SQL statement that works.

select act, 
       RANK() OVER(ORDER BY year DESC) 
from keessattbl 
where sat = 1010 and INT(year) <= 2014 
FETCH FIRST ROW ONLY

Is this the most efficient way to handle this.

Thanks in advance Doug

Answer 1

Another option would be to use the following:

select k1.*
from keessattbl k1
where k1.sat = 1010
and k1.year = (select max(k2.year) 
               from keessattbl k2
               where k2.sat = k1.sat
                 and k2.year <= 2014)

You will need to check which one is more efficient. If year (and possibly sat) is indexed, then both are probably quite fast.

But you will need to look at the execution plan (or simply time the statements) to find out.