COUNT

Returns the number of rows matching the query criteria.

SELECT COUNT(*) FROM Contacts WHERE FirstName = 'Bob'

COUNT(DISTINCT)

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

SELECT COUNT(DISTINCT LastName) AS DistinctValues FROM Contacts WHERE FirstName = 'Bob'

AVG

Returns the average of the column values.

SELECT Email, AVG(AnnualRevenue) FROM Contacts WHERE FirstName = 'Bob'  GROUP BY Email

MIN

Returns the minimum column value.

SELECT MIN(AnnualRevenue), Email FROM Contacts WHERE FirstName = 'Bob' GROUP BY Email

MAX

Returns the maximum column value.

SELECT Email, MAX(AnnualRevenue) FROM Contacts WHERE FirstName = 'Bob' GROUP BY Email

SUM

Returns the total sum of the column values.

SELECT SUM(AnnualRevenue) FROM Contacts WHERE FirstName = 'Bob'