Understanding the 'BETWEEN' Operator in SQL

The 'BETWEEN' operator in SQL is a logical operator that's primarily used to check if a value lies within a certain range. It facilitates filtering of query results within a specified range, improving your control over the data retrieved.

The 'BETWEEN' operator is not just limited to numeric values. You can also use it with dates and text (in alphabetical order).

Let's take a look at a practical example to understand how it works:

SELECT * FROM Employees
WHERE Salary BETWEEN 30000 AND 50000;

In this SQL statement, we're selecting all records from the 'Employees' table where the 'Salary' falls between 30000 and 50000. Here, the 'BETWEEN' operator checks if a 'Salary' value lies within this specified range.

Moreover, 'BETWEEN' operator is inclusive, meaning the end points (in this case 30000 and 50000) are included in the range. So, an employee with a salary exactly 30000 or exactly 50000 would be included in the result set.

A crucial best practice to remember when using the 'BETWEEN' operator is to always ensure that the lower boundary is written before the upper boundary, or else, no rows would be returned. This is because SQL evaluates the 'BETWEEN' clause from left to right, so the value on the left should be less than or equal to the value on the right.

It's also worth noting that you can use the 'NOT BETWEEN' operator if you want to select values outside of a specific range. This is particularly beneficial when you want to exclude a certain range of data from your result set.

In summary, the 'BETWEEN' operator is a versatile tool that allows you to efficiently filter your data based on certain criteria, enhancing the readability and manageability of your SQL queries. Remember to carefully define your range parameters to ensure accurate results.