SQL Server SUM

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

The SQL Server SUM() function is an aggregate function that calculates the sum of all or distinct values in an expression.

The syntax of the SUM() function is as follows:

SUM([ALL | DISTINCT ] expression)
Code language: SQL (Structured Query Language) (sql)

In this syntax:

  • ALL instructs the SUM() function to return the sum of all values including duplicates. ALL is used by default.
  • DISTINCT instructs the SUM() function to calculate the sum of the only distinct values.
  •  expression is any valid expression that returns an exact or approximate numeric value. Note that aggregate functions or subqueries are not accepted in the expression.

The SUM() function ignores NULL values.

ALL vs. DISTINCT

Let’s create a new table for demonstration the difference between ALL and DISTINCT:

CREATE TABLE t(
    val INT
);

INSERT INTO t(val)
VALUES(1),(2),(3),(3),(4),(NULL),(5);

SELECT
    val
FROM
    t;
Code language: SQL (Structured Query Language) (sql)
SQL Server SUM function ALL vs DISTINCT

The following statement returns the sum of all values in the val column:

SELECT
    SUM(val) total
FROM
    t;
Code language: SQL (Structured Query Language) (sql)

The output is:

total
-----------
18
Warning: Null value is eliminated by an aggregate or other SET operation.

(1 row affected)Code language: PHP (php)

However, when we use the DISTINCT modifier, the SUM() function returns the sum of only unique values in the val column:

SELECT
    SUM(DISTINCT val) total
FROM
    t;
Code language: SQL (Structured Query Language) (sql)

Here is the output:

total
-----------
15
Warning: Null value is eliminated by an aggregate or other SET operation.

(1 row affected)Code language: PHP (php)

SQL Server SUM() function examples

Let’s take some practical examples of using the SUM() function.

A) Simple SQL Server SUM() function example

The following statement returns the total stocks of all products in all stores:

SELECT 
    SUM(quantity) total_stocks
FROM 
    production.stocks;
Code language: SQL (Structured Query Language) (sql)

The following shows the output:

total_stocks
------------
13511

(1 row affected)

B) SQL Server SUM() function with GROUP BY example

The following statement finds total stocks by store id:

SELECT
    store_id,
    SUM(quantity) store_stocks
FROM
    production.stocks
GROUP BY
    store_id;
Code language: SQL (Structured Query Language) (sql)

Here is the output:

SQL Server SUM function with GROUP BY example

In this example:

  • First, the GROUP BY clause divided the stocks by store id into groups.
  • Second, the SUM() function is applied to each group to calculate the total stocks for each.

If you want to display the store name instead of store id, you can use the following statement:

SELECT
    store_name,
    SUM(quantity) store_stocks
FROM
    production.stocks w
    INNER JOIN sales.stores s
        ON s.store_id = w.store_id
GROUP BY
    store_name;
Code language: SQL (Structured Query Language) (sql)

The following picture shows the output:

SQL Server SUM function with GROUP BY and JOIN example

C) SQL Server SUM() function with HAVING clause example

The following statement finds stocks for each product and returns only products whose stocks are greater than 100:

SELECT
    product_name,
    SUM(quantity) total_stocks
FROM
    production.stocks s
    INNER JOIN production.products p
        ON p.product_id = s.product_id
GROUP BY
    product_name
HAVING
    SUM(quantity) > 100
ORDER BY
    total_stocks DESC;
Code language: SQL (Structured Query Language) (sql)

Here is the output:

SQL Server SUM function with GROUP BY and HAVING example

D) SQL Server SUM() function with expression example

The following example uses an expression in the SUM() function to calculate the net value for each sales order:

SELECT
    order_id,
    SUM(
        quantity * list_price * (1 - discount)
    ) net_value
FROM
    sales.order_items
GROUP BY
    order_id
ORDER BY
    net_value DESC;
Code language: SQL (Structured Query Language) (sql)

The output is as follows:

SQL Server SUM function with expression example

In this tutorial, you have learned how to use the SQL Server SUM() function to calculate the sum of values.

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