COUNT

Returns the number of rows matching the query criteria.

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

COUNT(DISTINCT)

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

SELECT COUNT(DISTINCT Id) AS DistinctValues FROM Lead WHERE FirstName <> 'Bob'

AVG

Returns the average of the column values.

SELECT FirstName, AVG(Revenue) FROM Lead WHERE FirstName <> 'Bob'  GROUP BY FirstName

MIN

Returns the minimum column value.

SELECT MIN(Revenue), FirstName FROM Lead WHERE FirstName <> 'Bob' GROUP BY FirstName

MAX

Returns the maximum column value.

SELECT FirstName, MAX(Revenue) FROM Lead WHERE FirstName <> 'Bob' GROUP BY FirstName

SUM

Returns the total sum of the column values.

SELECT SUM(Revenue) FROM Lead WHERE FirstName = 'Bob'