select *
from billboard
where group ilike '%Dr.Dre%' AND (year<2001 or year>2009);

select *
from billboard
where "group" ilike '%T-Pain%'
order by rank DESC;

select COUNT(low) as low_count
from apple;

COUNT(column name) only counts non null rows

SUM only use for numerical values, null will be see as 0

AVG calculates the average of a selected group of values AVG(column name), ignore null completely

select AVG(daily) as avg_volumn
from apple;