MySQL SUM() function

Summary: in this tutorial, you will learn how to use the MySQL SUM() function to calculate the sum of values in a set.

Introduction to the MySQL SUM() function

The SUM() function is an aggregate function that allows you to calculate the sum of values in a set. The syntax of the SUM() function is as follows:

SUM(DISTINCT expression)Code language: SQL (Structured Query Language) (sql)

Here is how the SUM() function works:

• If you use the SUM() function in a SELECT statement that returns no row, the SUM() function returns NULL, not zero.
• The DISTINCT option directs the SUM() function to calculate the sum of unique values in a set.
• The SUM() function ignores the NULL values in the calculation.

MySQL SUM() function illustration

First, create a new table called sum_demo:

CREATE TABLE sum_demo (
    n INT
);Code language: SQL (Structured Query Language) (sql)

The sum_demo table includes one column called n with the type INT.

Then, insert some rows into the sum_demo table:

INSERT INTO sum_demo(n)
VALUES
  (1),
  (1),
  (2),
  (NULL),
  (3);Code language: SQL (Structured Query Language) (sql)

Third, calculate the total values in the n column using the SUM() function:

SELECT
    SUM(n)
FROM
    sum_demo;Code language: SQL (Structured Query Language) (sql)

As you can see, the SUM() function calculates the total of 1, 1, 2, and 3. And it ignores NULL.

Finally, calculate the total unique values in the n column using the SUM() function with the DISTINCT option:

SELECT
    SUM(DISTINCT n)
FROM
    sum_demo;Code language: SQL (Structured Query Language) (sql)

In this case, the SUM() with the DISTINCT option calculates the sum of unique values which are 1, 2, and 3.

MySQL SUM() function examples

We’ll use the table orderdetails from the sample database.

1) Simple MySQL SUM() function example

This example uses the SUM() function to get the total number of items of the order details:

SELECT
    SUM(quantityOrdered) SalesQuantity
FROM
    orderdetails;Code language: SQL (Structured Query Language) (sql)

2) MySQL SUM() function with expression example

The following shows the order line items of the order number 10110:

SELECT
    orderNumber,
    quantityOrdered,
    priceEach
FROM
    orderdetails
WHERE
    orderNumber = 10100;Code language: SQL (Structured Query Language) (sql)

To calculate the total for the order number 10110, you use the SUM() function as follows:

SELECT
	SUM(quantityOrdered * priceEach)  orderTotal
FROM
	orderdetails
WHERE
	orderNumber = 10100;Code language: SQL (Structured Query Language) (sql)

In this example, the SUM() function calculates the total of the following expression of all order line items of order number 10110:

quantityOrdered * priceEachCode language: SQL (Structured Query Language) (sql)

3) MySQL SUM() with the GROUP BY clause example

The SUM() function is often used with the GROUP BY clause to calculate the sum for each group.

For example, you can calculate the total amount of each order by using the SUM()function with the GROUP BY clause as shown in the following query:

SELECT
    orderNumber,
    SUM(quantityOrdered * priceEach) orderTotal
FROM
    orderdetails
GROUP BY
    orderNumber
ORDER BY
    orderTotal DESC;Code language: SQL (Structured Query Language) (sql)

In this example:

• The GROUP BY clause divides order details into groups grouped by the order number.
• The SUM() function calculates the total of each amount in each order.

4) MySQL SUM() with HAVING clause example

You can use the SUM() function in the HAVING clause to filter the group. This example illustrates how to select orders whose order amounts are greater than 60,000.

SELECT
    orderNumber,
    SUM(quantityOrdered * priceEach) orderTotal
FROM
    orderdetails
GROUP BY
    orderNumber
HAVING
    SUM(quantityOrdered * priceEach) > 60000
ORDER BY
    orderTotal;Code language: SQL (Structured Query Language) (sql)

5) MySQL SUM() with NULL example

The SUM() function returns NULL if the result set is empty. Sometimes, you may want the SUM() function to return zero instead of NULL.

In this case, you can use the COALESCE() function. The COALESCE function accepts two arguments and returns the second argument if the first argument is NULL; otherwise, it returns the first argument.

See the following query:

SELECT
    COALESCE(SUM(quantityOrdered * priceEach), 0) result
FROM
    orderdetails
WHERE
    productCode = 'S1_20';Code language: SQL (Structured Query Language) (sql)

6) MySQL SUM() with join example

See the following orders and orderdetails tables:

You can use the SUM() function in a SELECT with JOIN clause to calculate the sum of values in a table based on a condition specified by the values in another table.

This statement uses the SUM() function to calculate the total amounts of the canceled orders:

SELECT
    SUM(quantityOrdered * priceEach) cancelled_amount
FROM
    orderdetails
INNER JOIN orders USING (orderNumber)
WHERE
    status = 'Cancelled';Code language: SQL (Structured Query Language) (sql)

7) MySQL SUM IF example

The following statement uses the SUM() function to calculate the number of items sold for each order status:

SELECT
    status,
    SUM(quantityOrdered)
FROM
    orderdetails
        INNER JOIN
    orders USING (orderNumber)
GROUP BY status;
Code language: SQL (Structured Query Language) (sql)

If you want to rotate rows to columns, you can use the SUM() function with CASEexpression. It is kind of SUMIF logic:

Summary

• Use the MySQL SUM() function to calculate the sum of values in a set.