10. Video: 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 NULLs 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.