Question

Is there a way to get multiple counts depending on multiple conditions from the same table?
eg. Count for when Days is less than 15, and count for days between 15 and 30.

Answer 1

Yes, you can combine SUM and CASE:

SELECT
    SUM(CASE WHEN condition1 THEN 1 ELSE 0 END) count1,
    SUM(CASE WHEN condition2 THEN 1 ELSE 0 END) count2
FROM yourtable

So for your specific example:

SELECT
    SUM(CASE WHEN days < 15 THEN 1 ELSE 0 END) count1,
    SUM(CASE WHEN days BETWEEN 15 AND 30 THEN 1 ELSE 0 END) count2
FROM yourtable

If the majority of rows have days > 30 it might be worth adding a WHERE days <= 30 to the end of the query as an optimization. Also be aware that BETWEEN includes both its end points.