COUNT

Returns the number of rows matching the query criteria.

SELECT COUNT(*) FROM Invoices WHERE Status = 'SENT'

COUNT(DISTINCT)

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

SELECT COUNT(DISTINCT Id) AS DistinctValues FROM Invoices WHERE Status = 'SENT'

AVG

Returns the average of the column values.

SELECT DueDate, AVG(AnnualRevenue) FROM Invoices WHERE Status = 'SENT'  GROUP BY DueDate

MIN

Returns the minimum column value.

SELECT MIN(AnnualRevenue), DueDate FROM Invoices WHERE Status = 'SENT' GROUP BY DueDate

MAX

Returns the maximum column value.

SELECT DueDate, MAX(AnnualRevenue) FROM Invoices WHERE Status = 'SENT' GROUP BY DueDate

SUM

Returns the total sum of the column values.

SELECT SUM(AnnualRevenue) FROM Invoices WHERE Status = 'SENT'