Visual Basic® .NET Database Programming

Aggregate Functions

Aggregate functions perform an operation on a group of values taken from a series of records. For example, the AVG function computes the average of a field’s value over the selected records. The following statement calculates the average Score value for records with StudentId value 1001:

SELECT AVG(Score) 
FROM Scores 
WHERE StudentId = 1001 

Table A.3 describes aggregate functions available in SQL Server.

Table A.3. Useful Aggregate Functions

Function	Purpose
AVG	Calculates the average of the selected values.
COUNT	Returns the number of selected records.
MAX	Returns the largest value selected.
MIN	Returns the smallest value selected.
SUM	Returns the sum of the selected values.
STDEV	Calculates the statistical standard deviation ...