Database Reference
In-Depth Information
▼
Input
SELECT SUM(item_price*quantity) AS total_price
FROM orderitems
WHERE order_num = 20005;
▼
Output
+-------------+
| total_price |
+-------------+
| 149.87 |
+-------------+
▼
Analysis
The function
SUM(item_price*quantity)
returns the sum of all the expanded
prices in an order, and again the
WHERE
clause ensures that just the correct order
items are included.
Tip
Performing Calculations on Multiple Columns All the aggregate functions can be used
to perform calculations on multiple columns using the standard mathematical operators,
as shown in the example.
Note
NULL
Values Column rows with
NULL
values in them are ignored by the
SUM()
function.
The five aggregate functions can all be used in two ways:
■
To perform calculations on all rows, specify the
ALL
argument, or
specify no argument at all (because
ALL
is the default behavior).
■
To only include unique values, specify the
DISTINCT
argument.
Tip
ALL
Is Default The
ALL
argument need not be specified because it is the default
behavior. If
DISTINCT
is not specified,
ALL
is assumed.
