# SUM

## Syntax

```sql
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`.

`SUM()` can be used as a [window function](https://mariadb.com/docs/server/reference/sql-functions/special-functions/window-functions), although not with the `DISTINCT` specifier.

## Examples

```sql
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](https://mariadb.com/docs/server/sql-statements/data-manipulation/selecting-data/select#group-by) clause:

```sql
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](https://mariadb.com/docs/server/sql-statements/data-manipulation/selecting-data/select#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:

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

As a [window function](https://mariadb.com/docs/server/reference/sql-functions/special-functions/window-functions):

```sql
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](https://mariadb.com/docs/server/reference/sql-functions/aggregate-functions/avg) (average)
* [MAX](https://mariadb.com/docs/server/reference/sql-functions/aggregate-functions/max) (maximum)
* [MIN](https://mariadb.com/docs/server/reference/sql-functions/aggregate-functions/min) (minimum)

<sub>*This page is licensed: GPLv2, originally from*</sub> [<sub>*fill\_help\_tables.sql*</sub>](https://github.com/MariaDB/server/blob/main/scripts/fill_help_tables.sql)

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