COUNT

Returns the number of rows matching the query criteria.

SELECT COUNT(*) FROM Orders WHERE BuyerEmail = 'bob@gmail.com'

COUNT(DISTINCT)

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

SELECT COUNT(DISTINCT Id) AS DistinctValues FROM Orders WHERE BuyerEmail = 'bob@gmail.com'

AVG

Returns the average of the column values.

SELECT SellerOrderId, AVG(AnnualRevenue) FROM Orders WHERE BuyerEmail = 'bob@gmail.com'  GROUP BY SellerOrderId

MIN

Returns the minimum column value.

SELECT MIN(AnnualRevenue), SellerOrderId FROM Orders WHERE BuyerEmail = 'bob@gmail.com' GROUP BY SellerOrderId

MAX

Returns the maximum column value.

SELECT SellerOrderId, MAX(AnnualRevenue) FROM Orders WHERE BuyerEmail = 'bob@gmail.com' GROUP BY SellerOrderId

SUM

Returns the total sum of the column values.

SELECT SUM(AnnualRevenue) FROM Orders WHERE BuyerEmail = 'bob@gmail.com'