COUNT

Returns the number of rows matching the query criteria.

SELECT COUNT(*) FROM Repositories WHERE OwnerLogin = 'mojombo'

COUNT(DISTINCT)

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

SELECT COUNT(DISTINCT Name) AS DistinctValues FROM Repositories WHERE OwnerLogin = 'mojombo'

AVG

Returns the average of the column values.

SELECT OwnerLogin, AVG(Size) FROM Repositories WHERE OwnerLogin = 'mojombo'  GROUP BY OwnerLogin

MIN

Returns the minimum column value.

SELECT MIN(Size), OwnerLogin FROM Repositories WHERE OwnerLogin = 'mojombo' GROUP BY OwnerLogin

MAX

Returns the maximum column value.

SELECT OwnerLogin, MAX(Size) FROM Repositories WHERE OwnerLogin = 'mojombo' GROUP BY OwnerLogin

SUM

Returns the total sum of the column values.

SELECT SUM(Size) FROM Repositories WHERE OwnerLogin = 'mojombo'