10. Video: AVG
AVG
Similar to other software AVG returns the mean of the data - that is the sum of all of the values in the column divided by the number of values in a column. This aggregate function again ignores the NULL values in both the numerator and the denominator.
If you want to count NULL s as zero, you will need to use SUM and COUNT . However, this is probably not a good idea if the NULL values truly just represent unknown values for a cell.
MEDIAN - Expert Tip
One quick note that a median might be a more appropriate measure of center for this data, but finding the median happens to be a pretty difficult thing to get using SQL alone — so difficult that finding a median is occasionally asked as an interview question.