SQL Server Arithmetic Operators

This SQL tutorial focuses on SQL Server Arithmetic Operators, and provides explanations, examples, and exercises. For this lesson’s exercises, use this link.

This tutorial is a part of several posts explaining how to write basic queries in SQL Server. To read additional posts regarding this subject, please use the following links:

SQL Server Arithmetic Operators

You may not always want to retrieve the data as is. In some cases, you may want to display your data with certain calculation, or look at a what-if scenarios (for example, you may want to know how the prices would look like after adding VAT).

Arithmetic Operations on Numeric Values

This SQL Server example calculates the employee’s salary after an addition of 20%.

```SELECT last_name , first_name, salary,  salary * 1.2
FROM   employees
```

It is advisable to specify the original column without the change (salary) in addition to the column with the calculation (salary *1.2), in order to make the difference – in this example, the increase – visible.

It is possible to perform any mathematical calculation:

```SELECT last_name , first_name , salary,
salary * 0.14 / 2.74 + 52.36
FROM   employees
```

In order to define operator precedence, simply use round brackets:

```SELECT last_name , first_name , salary,
salary * 0.14 / (2.74 + 52.36)
FROM   employees
```

In SQL Server, You can also use arithmetic operators on multiple columns:

```SELECT ProductName , ProductPrice , Discount
ProductPrice - Discount
FROM   products
```

Note : SQL Server syntax Ignores blank spaces before and after the arithmetic operator.

Arithmetic Operations on String Values

In SQL Server It is not possible to perform any calculations on String values (such as Varchar or Char).

```SELECT last_name , first_name + 300
FROM employees

(error)
```

Arithmetic Operations on Date Values

In SQL Server The plus (+) and minus (-) operators can be used to perform arithmetic operations on Date values. These operators will allow you to add or subtract days.

```SELECT last_name , first_name , hire_date, hire_date + 1
FROM employees
```

Result: Worker’s employment date (+) one day

```SELECT last_name , first_name , hire_date, hire_date - 1
FROM employees
```

Result: Worker’s employment date (-) one day

In SQL Server It is not possible to carry out any calculation of (multiplication) or (division) on Date values.

```SELECT last_name , first_name , hire_date,  hire_date * 3
FROM employees
(error)

SELECT last_name , first_name , hire_date, hire_date / 7
FROM employees
(error)
```

Arithmetic Operations on NULL Values

In SQL Server A NULL value is a value that indicates an empty field in a table. This value does not equal zero (0), nor does it equal space (‘ ‘); When a certain calculation is carried out on a column that contains NULL values, any calculation performed on the NULL value returns NULL.

```SELECT last_name, salary, commission_pct,
commission_pct + 1
FROM employees

SELECT last_name, salary, commission_pct ,
salary * commission_pct
FROM employees
```

The commission_pct column is a column that contains NULL values. Each calculation on a field in this column that contains NULL value returns NULL.

General Guidelines

• In SQL Server calculations on columns (of any data type) do not modify the contents (actual data) of the column in the table, but only display the column’s contents for that specific query, in another way.
• In SQL Server Calculations on columns change the column’s header’s in the output (this issue will be addressed in the next post – Column Aliases)
```SELECT last_name, salary, salary  + 500
FROM employees
```

Result :

```last_name    salary   (No Column Name)
------------ ------   ----------------
Doe           5700     6200
```

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