Left Outer Join doesn't return all rows from my left table?

Question

I am trying to get the number of page opens on a per day basis using the following query.

SELECT day.days, COUNT(*) as opens 
FROM day 
LEFT OUTER JOIN track         


        

Answer 1

The condition is in the WHERE clause. After joining the tables the WHERE conditions are evaluated to filter out everything matching the criteria.Thus anything not matching tracking.open_id = 10 gets discarded.

If you want to apply this condition while joining the two tables, a better way is to use it with the ON clause (i.e. joining condition) than the entire dataset condition.