Syntax

SUM([DISTINCT] expr)

Description

Returns the sum of expr. If the return set has no rows, SUM() returns NULL. The DISTINCT keyword can be used to sum only the distinct values of expr.

From MariaDB 10.2.0, SUM() can be used as a window function, although not with the DISTINCT specifier.

Examples

CREATE TABLE sales (sales_value INT);
INSERT INTO sales VALUES(10),(20),(20),(40);

SELECT SUM(sales_value) FROM sales;
+------------------+
| SUM(sales_value) |
+------------------+
|               90 |
+------------------+

SELECT SUM(DISTINCT(sales_value)) FROM sales;
+----------------------------+
| SUM(DISTINCT(sales_value)) |
+----------------------------+
|                         70 |
+----------------------------+

Commonly, SUM is used with a GROUP BY clause:

CREATE TABLE sales (name CHAR(10), month CHAR(10), units INT);

INSERT INTO sales VALUES 
  ('Chun', 'Jan', 75), ('Chun', 'Feb', 73),
  ('Esben', 'Jan', 43), ('Esben', 'Feb', 31),
  ('Kaolin', 'Jan', 56), ('Kaolin', 'Feb', 88),
  ('Tatiana', 'Jan', 87), ('Tatiana', 'Feb', 83);

SELECT name, SUM(units) FROM sales GROUP BY name;
+---------+------------+
| name    | SUM(units) |
+---------+------------+
| Chun    |        148 |
| Esben   |         74 |
| Kaolin  |        144 |
| Tatiana |        170 |
+---------+------------+

The GROUP BY clause is required when using an aggregate function along with regular column data, otherwise the result will be a mismatch, as in the following common type of mistake:

SELECT name,SUM(units) FROM sales
;+------+------------+
| name | SUM(units) |
+------+------------+
| Chun |        536 |
+------+------------+

As a window function:

CREATE OR REPLACE TABLE student_test (name CHAR(10), test CHAR(10), score TINYINT);
INSERT INTO student_test VALUES 
    ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), 
    ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), 
    ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), 
    ('Tatiana', 'SQL', 87);

SELECT name, test, score, SUM(score) OVER (PARTITION BY name) AS total_score FROM student_test;
+---------+--------+-------+-------------+
| name    | test   | score | total_score |
+---------+--------+-------+-------------+
| Chun    | SQL    |    75 |         148 |
| Chun    | Tuning |    73 |         148 |
| Esben   | SQL    |    43 |          74 |
| Esben   | Tuning |    31 |          74 |
| Kaolin  | SQL    |    56 |         144 |
| Kaolin  | Tuning |    88 |         144 |
| Tatiana | SQL    |    87 |          87 |
+---------+--------+-------+-------------+

See Also

• AVG (average)
• MAX (maximum)
• MIN (minimum)