COUNT

Returns the number of rows matching the query criteria.

SELECT COUNT(*) FROM Orders WHERE ShipCountry = 'USA'

COUNT(DISTINCT)

Returns the number of distinct, non-null field values matching the query criteria.

SELECT COUNT(DISTINCT ShipName) AS DistinctValues FROM Orders WHERE ShipCountry = 'USA'

AVG

Returns the average of the column values.

SELECT ShipCity, AVG(Freight) FROM Orders WHERE ShipCountry = 'USA'  GROUP BY ShipCity

MIN

Returns the minimum column value.

SELECT MIN(Freight), ShipCity FROM Orders WHERE ShipCountry = 'USA' GROUP BY ShipCity

MAX

Returns the maximum column value.

SELECT ShipCity, MAX(Freight) FROM Orders WHERE ShipCountry = 'USA' GROUP BY ShipCity

SUM

Returns the total sum of the column values.

SELECT SUM(Freight) FROM Orders WHERE ShipCountry = 'USA'