# SQLite Expressions

Expressions are the building blocks of SQLite queries. They are used to calculate results, manipulate data, and create new values based on existing data. In SQLite, expressions can include literal values, column references, operators, and functions.

## Syntax

The basic syntax for expressions in SQLite is as follows:

```
SELECT expression1, expression2, ... expressionN FROM table_name;
```

The expressions can be composed of any valid combination of data types, columns, operators, and functions.

## Example

Suppose we have a table called `employees`

with columns for `employee_id`

, `first_name`

, `last_name`

, `salary`

, and `department`

. We can use expressions to select all employees with a salary greater than $50,000 and calculate their annual salaries.

```
SELECT first_name, last_name, salary, salary * 12 as annual_salary
FROM employees
WHERE salary > 50000;
```

## Output

The output of the above example would be a table of employees with their first name, last name, salary, and calculated annual salary for all employees with a salary greater than $50,000.

```
first_name | last_name | salary | annual_salary
-----------+-----------+--------+--------------
John | Doe | 75000 | 900000
Jane | Smith | 60000 | 720000
Bob | Johnson | 55000 | 660000
```

## Explanation

In the example above, we use an expression to create a new value by multiplying the employee's salary by 12 to calculate their annual salary. We select only those employees whose salary is greater than $50,000 using the `WHERE`

clause to filter the results.

## Use

Expressions are used to calculate, transform, and manipulate data in SQLite queries. They can be used to create new values based on existing data, perform calculations on numeric data, manipulate strings, and more. Expressions are used extensively in SQL to retrieve, insert, update, and delete data.

## Important Points

- Expressions can include literals, columns, operators, and functions.
- SQLite supports a wide variety of functions, including mathematical, string, date and time functions, aggregate functions, and more.
- The
`SELECT`

statement in SQLite can include any number of expressions separated by commas. - In SQLite, expressions are evaluated left to right, with the exception of unary operators which are evaluated right to left.
- Parentheses can be used to control the order of evaluation.

## Summary

In this tutorial, we learned about expressions in SQLite and how they are used to create new values, manipulate data, and perform calculations. We saw an example of using expressions to select employees with a salary greater than $50,000 and calculate their annual salaries. Expressions are an essential part of SQL queries and are used extensively to retrieve, insert, update, and delete data.