COUNT

Returns the number of rows matching the query criteria.

SELECT COUNT(*) FROM [adventureworks].[Model].Customer WHERE Country = 'Australia'

COUNT(DISTINCT)

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

SELECT COUNT(DISTINCT Country) AS DistinctValues FROM [adventureworks].[Model].Customer WHERE Country = 'Australia'

AVG

Returns the average of the column values.

SELECT Education, AVG(AnnualRevenue) FROM [adventureworks].[Model].Customer WHERE Country = 'Australia'  GROUP BY Education

MIN

Returns the minimum column value.

SELECT MIN(AnnualRevenue), Education FROM [adventureworks].[Model].Customer WHERE Country = 'Australia' GROUP BY Education

MAX

Returns the maximum column value.

SELECT Education, MAX(AnnualRevenue) FROM [adventureworks].[Model].Customer WHERE Country = 'Australia' GROUP BY Education

SUM

Returns the total sum of the column values.

SELECT SUM(AnnualRevenue) FROM [adventureworks].[Model].Customer WHERE Country = 'Australia'