MySQL COUNT(), AVG() and SUM() Functions
MySQL COUNT(), AVG() and SUM() Functions
The COUNT() function returns the number of rows that matches a specified criterion.
COUNT() Syntax
SELECT COUNT(column_name)
FROM table_name
WHERE condition;
FROM table_name
WHERE condition;
The AVG() function returns the average value of a numeric column.
AVG() Syntax
SELECT AVG(column_name)
FROM table_name
WHERE condition;
FROM table_name
WHERE condition;
The SUM() function returns the total sum of a numeric column.
SUM() Syntax
SELECT SUM(column_name)
FROM table_name
WHERE condition;
FROM table_name
WHERE condition;
Demo Database
Below is a selection from the "Products" table in the Northwind sample database:
| ProductID | ProductName | SupplierID | CategoryID | Unit | Price |
|---|---|---|---|---|---|
| 1 | Chais | 1 | 1 | 10 boxes x 20 bags | 18 |
| 2 | Chang | 1 | 1 | 24 - 12 oz bottles | 19 |
| 3 | Aniseed Syrup | 1 | 2 | 12 - 550 ml bottles | 10 |
| 4 | Chef Anton's Cajun Seasoning | 2 | 2 | 48 - 6 oz jars | 22 |
| 5 | Chef Anton's Gumbo Mix | 2 | 2 | 36 boxes | 21.35 |
COUNT() Example
The following SQL statement finds the number of products:
Note: NULL values are not counted.
AVG() Example
The following SQL statement finds the average price of all products:
Note: NULL values are ignored.
Demo Database
Below is a selection from the "OrderDetails" table in the Northwind sample database:
| OrderDetailID | OrderID | ProductID | Quantity |
|---|---|---|---|
| 1 | 10248 | 11 | 12 |
| 2 | 10248 | 42 | 10 |
| 3 | 10248 | 72 | 5 |
| 4 | 10249 | 14 | 9 |
| 5 | 10249 | 51 | 40 |
SUM() Example
The following SQL statement finds the sum of the "Quantity" fields in the "OrderDetails" table:
Note: NULL values are ignored.