In [SQL](https://www.educative.io/answers/sql-vs-plsql), the aggregate function `SUM()` adds a set of numbers (either in a given column or returned by some expression) and returns the summation value. It can be used in different ways. We can use it with multiple clauses, expressions, and numbers.  

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

```SQL
SELECT SUM(expression) FROM table_name;
```

## Parameter(s)
This function receives only one parameter:
- `expression`: It could be a set of column values or a mathematical expression.

## Return value(s)
This function returns the summation value.

## Examples
Consider the following table for upcoming examples:

Persons

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### Example 1: Using `SUM()` with one column
If we want to sum the `Salary` column, we can write the query as follow:

SELECT SUM(Salary) AS total_salary FROM Persons;

### Example 2: Using `SUM()` with the `WHERE` clause
If we want to sum the salary of people of `Lahore` city, we can write the query as follow:

SELECT SUM(Salary) AS lahore_salary 
FROM Persons
WHERE City='Lahore';

### Example 3: Using `SUM()` with the `GROUP BY` clause
If we want to sum the salary of each city, we can write the query as follow:

SELECT City, SUM(Salary) AS total_salary 
FROM Persons
GROUP BY City;

### Example 4: Using `SUM()` with a mathematical  expression
In the `SUM()` function, we can perform mathematical operations with the returned values of a column. For example, the following query will half the summation value of the `Salary` column: 

SELECT SUM(Salary/2) AS half_of_total_salary FROM Persons;

Suppose we pass a numeric value, i.e., 2, -5, etc., or an expression that results in a numeric value, i.e., 5+3, 1/2, etc., the `SUM()` function will multiply the numeric values with the number of rows returned by the rest of the query.


SELECT SUM(2) AS double_of_total FROM Persons;
SELECT SUM(1/2) AS half_of_total FROM Persons; 

SELECT SUM(1) AS total_number_of_males FROM Persons WHERE Gender='Male';
SELECT SUM(1) AS total_number_of_taxables FROM Persons WHERE Salary >= 60000;

### Explanation

- **Line 1:** The first query returns the number of rows multiplied by `2`. The `SUM(2)` function returns `14`.

- **Line 2:** This query returns the number of rows multiplied by `1/2`. The `SUM(1/2)` function returns `3.5000`.

- **Line 4:** The `SUM(1)` multiplies the number of rows returned by the `WHERE` clause with `1` and returns the results. This query returns the number of males in the `Person` table. The output is `4`.

- **Line 5:** In this query, `SUM(1)` returns the number of employees having a salary more or equal to `60000`. The result is `5`.


How to use SUM() in SQL

Use SQL's SUM() function to add numbers in a column or expression, supporting various clauses.

ID	Name	Gender	City	Salary
1	Ali	Male	Lahore	50000
2	Basit	Male	Okara	55000
3	Sana	Female	Lahore	70000
4	Dua	Female	Lahore	60000
5	Raza	Male	Karachi	65000
6	Saba	Female	Karachi	63000
7	Riaz	Male	Lahore	60000

How to use SUM() in SQL

Syntax

Parameter(s)

Return value(s)

Examples

Persons

Example 1: Using SUM() with one column

Example 2: Using SUM() with the WHERE clause

Example 3: Using SUM() with the GROUP BY clause

Example 4: Using SUM() with a mathematical expression

Explanation

Example 1: Using `SUM()` with one column

Example 2: Using `SUM()` with the `WHERE` clause

Example 3: Using `SUM()` with the `GROUP BY` clause

Example 4: Using `SUM()` with a mathematical expression