COUNT

Returns the number of rows matching the query criteria.

SELECT COUNT(*) FROM Customers WHERE CompanyName = 'CompanyName'

COUNT(DISTINCT)

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

SELECT COUNT(DISTINCT CustNum) AS DistinctValues FROM Customers WHERE CompanyName <> 'CompanyName'

AVG

Returns the average of the column values.

SELECT Company, AVG(AnnualRevenue) FROM Customers WHERE CompanyName <> 'CompanyName'  GROUP BY Company

MIN

Returns the minimum column value.

SELECT MIN(AnnualRevenue), Company FROM Customers WHERE CompanyName <> 'CompanyName' GROUP BY Company

MAX

Returns the maximum column value.

SELECT Company, MAX(AnnualRevenue) FROM Customers WHERE CompanyName <> 'CompanyName' GROUP BY Company

SUM

Returns the total sum of the column values.

SELECT SUM(AnnualRevenue) FROM Customers WHERE CompanyName = 'CompanyName'