SELECT COUNT(*) FROM weather WHERE mean_humidity  >  50 AND mean_visibility_miles  >  8
How many days had both mean humidity above 50 and mean visibility above 8?
SELECT COUNT ( * ) FROM weather WHERE mean_humidity > 50 AND mean_visibility_miles > 8
select count ( * ) from weather where mean_humidity > value and mean_visibility_miles > value
How many days had both mean humidity above 50 and mean visibility above 8 ?