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.
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 ... |
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