# SUM

In SQL, the ** SUM()** function is an aggregate function used to calculate the sum of values in a specified column of a table or the sum of a set of numerical values.

## Basic syntax

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

```
SELECT SUM(column_name)
FROM table_name
WHERE condition
```

: This calculates the sum of values in the specified`SUM(column_name)`

.`column_name`

: This is the name of the table from which you want to retrieve the data.`table_name`

: This is an optional condition that specifies which rows to include in the sum calculation.`condition`

## Examples

Consider a table named ** sales** with the following structure and data:

sales_id | product_id | quantity | amount |
---|---|---|---|

1 | 101 | 2 | 100 |

2 | 102 | 3 | 150 |

3 | 101 | 1 | 50 |

4 | 103 | 2 | 120 |

To calculate the total amount of sales, you can use the ** SUM()** function as follows:

```
SELECT SUM(amount) AS total_sales
FROM sales
```

This query will return the sum of the ** amount** column, which is

**, representing the total sales amount.**

`420`

## Subtraction

SQL does not have a specific "subtract" function, but subtraction is achieved using the minus (-) operator. The minus operator is used to subtract one numeric value from another.

### Syntax:

```
SELECT column1 - column2 AS result
FROM your_table;
```

### Example:

```
SELECT 10 - 5 AS subtraction_result;
-- Output: 5
SELECT column1, column2, column1 - column2 AS subtraction_result
FROM your_table;
```

You can also perform subtraction with column values or variables, and you can use parentheses to control the order of operations if needed.

**Example with Column Values:**

```
SELECT column1, column2, (column1 - column2) AS subtraction_result
FROM your_table;
```

It's important to note that subtraction works with both integers and floating-point numbers. If you subtract two integers, the result will be an integer. If at least one operand is a floating-point number, the result will be a floating-point number.

```
SELECT 7 - 3 AS integer_subtraction;
-- Output: 4
SELECT 7.0 - 3.5 AS float_subtraction;
-- Output: 3.5
```