SQL SUM(): Add Up Values in a Column

SUM adds up the values in a column: total revenue, total payroll, total units in stock. Like COUNT, it is an aggregate function that turns many rows into a single number.

The example tables#

employees

orders

Syntax#

SELECT SUM(column)
FROM table_name
WHERE condition;

SUM only works on numeric columns.

Total of a column#

SELECT SUM(salary) AS total_payroll
FROM employees;

total_payroll
-------------
318000

Total of matching rows#

Revenue from February onwards:

SELECT SUM(amount) AS revenue
FROM orders
WHERE order_date >= '2026-02-01';

revenue
-------
770

That is 120 + 560 + 90. Order 101 from January was filtered out before summing.

Sum of a calculation#

SUM can add up any expression, evaluated row by row. The total value of stock in the products table is each product's price times its stock, summed:

SELECT SUM(price * stock) AS stock_value
FROM products;

stock_value
-----------
868500

Sum per group#

SELECT department, SUM(salary) AS payroll
FROM employees
GROUP BY department
ORDER BY payroll DESC;

department  | payroll
------------+--------
Engineering | 159000
Sales       | 113000
Marketing   | 46000

When no rows match, SUM returns NULL#

SELECT SUM(amount) AS revenue
FROM orders
WHERE amount > 1000;

revenue
-------
NULL

There is nothing to add, so the answer is "unknown", not zero. In reports you usually want 0; wrap it with COALESCE:

SELECT COALESCE(SUM(amount), 0) AS revenue
FROM orders
WHERE amount > 1000;

SUM also skips NULL values inside the column, so a missing value is treated as "not there" rather than as zero.

Conditional sums#

Put a CASE expression inside SUM to total only some rows while still looking at all of them. This counts Sales employees by adding 1 for each:

SELECT SUM(CASE WHEN department = 'Sales' THEN 1 ELSE 0 END) AS sales_people
FROM employees;

sales_people
------------
2

The same idea builds side-by-side totals: SUM(CASE WHEN region = 'North' THEN revenue ELSE 0 END) AS north, SUM(CASE WHEN region = 'South' THEN revenue ELSE 0 END) AS south.

Common mistakes#

Practice#

SELECT category, SUM(price * stock) AS stock_value
FROM products
GROUP BY category
ORDER BY stock_value DESC;

category    | stock_value
------------+------------
Electronics | 760000
Furniture   | 78500
Stationery  | 30000

Key takeaway#