How to Calculate the Difference Between Two Dates in SQL

Calculating the difference between two dates in SQL can be a tricky task. Whether you're trying to figure out how long it's been since a customer made a purchase or how much time has passed since an event occurred, you'll need to know how to calculate the difference between two dates in SQL. Luckily, there are a few simple techniques that can help you get the answer you need.

The Solution

The solution is to use the DATEDIFF() function. This function takes three arguments: the start date, the end date, and the unit of time you want to use for the calculation. For example, if you wanted to calculate the number of days between two dates, you would use the following query:

SELECT DATEDIFF(start_date, end_date, 'day') FROM table_name;

Examples

Let's look at a few examples of how this function can be used. Suppose you have a table called orders with the following data:

If you wanted to calculate the number of days between the first and third orders, you would use the following query:

SELECT DATEDIFF(order_date, '2020-03-01', 'day') FROM orders WHERE order_id = 1;

This query would return the result 59, since there are 59 days between the first and third orders.

Additional Info

The DATEDIFF() function is supported by most major databases, including MySQL, PostgreSQL, and SQL Server. However, the syntax may vary slightly depending on the database you are using. For more information, check out the documentation for your particular database. 🤓