10.7.1: Aggregate functions
- Page ID
- 93705
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Aggregate functions perform a calculation on a set of values and return a single, or summary, value. Table \(\PageIndex{1}\) lists these functions.
| FUNCTION | DESCRIPTION |
| AVG | Returns the average of all the values, or only the DISTINCT values, in the expression. |
| COUNT | Returns the number of non-null values in the expression. When DISTINCT is specified, COUNT finds the number of unique non-null values. |
| COUNT(*) | Returns the number of rows. COUNT(*) takes no parameters and cannot be used with DISTINCT. |
| MAX | Returns the maximum value in the expression. MAX can be used with numeric, character and datetime columns, but not with bit columns. With character columns, MAX finds the highest value in the collating sequence. MAX ignores any null values. |
| MIN | Returns the minimum value in the expression. MIN can be used with numeric, character and datetime columns, but not with bit columns. With character columns, MIN finds the value that is lowest in the sort sequence. MIN ignores any null values. |
| SUM | Returns the sum of all the values, or only the DISTINCT values, in the expression. SUM can be used with numeric columns only. |
Below are examples of each of the aggregate functions listed in Table \(\PageIndex{1}\).
Example #1: AVG
SELECT AVG (price) AS ‘Average Title Price’
FROM Books
Example #2: COUNT
SELECT COUNT(PubID) AS ‘Number of Publishers’
FROM Publishers
Example #3: COUNT
SELECT COUNT(province) AS ‘Number of Publishers’
FROM Publishers
Example #3: COUNT (*)
SELECT COUNT(*)
FROM Employees
WHERE job_lvl = 35
Example #4: MAX
SELECT MAX (HireDate)
FROM Employees
Example #5: MIN
SELECT MIN (price)
FROM Books
Example #6: SUM
SELECT SUM(discount) AS ‘Total Discounts’
FROM Discounts