In Redshift/Postgres, how to count rows that meet a condition?

Question

I\'m trying to write a query that count only the rows that meet a condition.

For example, in MySQL I would write it like this:

SELECT
    COUNT(IF(gr         


        

Answer 1

Another method:

SELECT 
    sum(CASE WHEN grade < 70 THEN 1 else 0 END) as grade_less_than_70,
    sum(CASE WHEN grade >= 70 and grade < 80 THEN 1 else 0 END) as grade_between_70_and_80
FROM
   grades

Works just fine in case you want to group the counts by a categorical column.