Question

I’m doing some statistics based on a database of states. I would like to output the rank of a state and it’s percentage as compared to the other states (i.e. state X’s value is higher then 55% of the other states’ value).

I’m trying something like this:

SELECT 
  count(*) AS TotalStates, 
  (SELECT COUNT(*) FROM states) AS NumberStates,
  (TotalStates/NumStates) AS percentage 
FROM states 
WHERE CRITERIA > 7.5

I’m getting an SQL error, TotalStates (my derived value) is not found. How can I get all three of these values returned with one query?

Answer 1

You can put the main calculations in a subselect, then reference the aliased columns in the outer query, both to pull the already calculated values and to obtain another one from them:

SELECT
  TotalStates,
  NumberStates,
  TotalStates / NumberStates AS percentage
FROM (
  SELECT 
    COUNT(*) AS TotalStates, 
    (SELECT COUNT(*) FROM states) AS NumberStates
  FROM states 
  WHERE CRITERIA > 7.5
) s