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AVG

Returns the average value within the requested window.

For more information on usage, please refer to Window Functions.

Syntax

AVG( <val> ) OVER ( [ PARTITION BY <exp> ] )
   
Parameter Description
<val> An expression used for the AVG() function.
<expr> An expression used for the partition by clause.

Example

The example below is querying test scores for students in various grade levels. Unlike a regular AVG() aggregation, the window function allows us to see how each student individually compares to the average test score for their grade level.

SELECT
	first_name,
	grade_level,
	test_score,
	AVG(test_score) OVER (PARTITION BY grade_level) AS average_for_grade
FROM
	class_test;

Returns:

' +------------+-------------+------------+-------------------------+
' | first_name | grade_level | test_score |    average_for_grade    |
' +------------+-------------+------------+-------------------------+
' | Frank      |           9 |         76 | 81.33333333333333       |
' | Humphrey   |           9 |         90 | 81.33333333333333       |
' | Iris       |           9 |         79 | 81.33333333333333       |
' | Sammy      |           9 |         85 | 81.33333333333333       |
' | Peter      |           9 |         80 | 81.33333333333333       |
' | Jojo       |           9 |         78 | 81.33333333333333       |
' | Brunhilda  |          12 |         92 | 89                      |
' | Franco     |          12 |         94 | 89                      |
' | Thomas     |          12 |         66 | 89                      |
' | Gary       |          12 |        100 | 89                      |
' | Charles    |          12 |         93 | 89                      |
' | Jesse      |          12 |         89 | 89                      |
' | Roseanna   |          11 |         94 | 73                      |
' | Carol      |          11 |         52 | 73                      |
' | Wanda      |          11 |         73 | 73                      |
' | Shangxiu   |          11 |         76 | 73                      |
' | Larry      |          11 |         68 | 73                      |
' | Otis       |          11 |         75 | 73                      |
' | Deborah    |          10 |         78 | 68.2                    |
' | Yolinda    |          10 |         30 | 68.2                    |
' | Albert     |          10 |         59 | 68.2                    |
' | Mary       |          10 |         85 | 68.2                    |
' | Shawn      |          10 |         89 | 68.2                    |
' +------------+-------------+------------+-------------------------+