SQL Query to Calculate Total Number of Days Between Two Specific Dates

Calculating the difference between dates is a common requirement in SQL, especially for tasks related to time tracking, project management, and historical data analysis. SQL provides various tools to work with date and time data, and one of the most straightforward is the DATEDIFF() function. This function allows us to efficiently compute the difference in days, or other units, between two dates.

In this article, we’ll explain how to calculate the total number of days between two specific dates using SQL, with the help of the DATEDIFF() function. We’ll also provide examples to demonstrate its usage step by step.

1. Using DATEDIFF() Function

The most straightforward method to calculate the difference in days between two dates in SQL is by using the DATEDIFF() function. This function returns the difference in days between the start date and the end date.

Syntax

DATEDIFF(day or dy or y, <start_date>, <end_date>);

Key Terms

• day: Specifies that the difference should be calculated in days.
• start_date: The starting date.
• end_date: The ending date.

Calculating Total Number of Days Between Two Specific Dates

Here, we will learn how to calculate the total number of days between two specific dates in SQL. To demonstrate the use of DATEDIFF(), let’s calculate the number of days between the purchase dates of two items from a sample orders table.

Step 1: Create a Demo Database and Table

First, we’ll create a database called geeks and a table named demo_orders, which contains details about various orders. Use the below SQL statement to create a database called geeks.

Query:

CREATE DATABASE geeks;
USE geeks;

CREATE TABLE demo_orders(
    ORDER_ID INT IDENTITY(1,1) PRIMARY KEY,
    ITEM_NAME VARCHAR(30) NOT NULL,
    ORDER_DATE DATE
);

INSERT INTO demo_orders
VALUES
    ('Maserati', '2007-10-03'),
    ('BMW', '2010-07-23'),
    ('Mercedes Benz', '2012-11-12'),
    ('Ferrari', '2016-05-09'),
    ('Lamborghini', '2020-10-20');

SELECT * FROM demo_orders;

Output

Step 2: Using DATEDIFF() to Calculate the Difference

Now let's find the number of days between the dates of the order of 'Maserati' and 'Ferrari' in the table using DATEDIFF() function. This result indicates that 3,136 days passed between the purchase dates of 'Maserati' and 'Ferrari'.

Query:

DECLARE 
@start VARCHAR(10) = (
  SELECT order_date FROM demo_orders
  WHERE item_name = 'Maserati'),
@end VARCHAR(10) = (
  SELECT order_date FROM demo_orders
  WHERE item_name = 'Ferrari')

--@start variable holds the start date(i.e date of Maserati being purchased).
--@end variable holds the end date (i.e date of Ferrari being purchased).

SELECT DATEDIFF(day, @start, @end) AS number_of_days;

Output

Explanation:

The @start variable stores the purchase date of 'Maserati' (2007-10-03), while the @end variable holds the purchase date of 'Ferrari' (2016-05-09). By using these two variables as inputs, the DATEDIFF() function calculates the difference in days between the two dates, providing a precise measure of the time interval. This approach simplifies date calculations by dynamically referencing specific dates from the database, ensuring accuracy and flexibility.

Comparing DATEDIFF with Other Methods

The DATEDIFF() function is not the only way to calculate date differences in SQL. However, it is often the most convenient and efficient.

Key Advantages:

• Simplicity: Easy to use with minimal syntax.
• Flexibility: Supports various date parts like days, months, and years.
• Accuracy: Handles leap years and varying month lengths automatically.

Example Use Cases:

• Calculating the age of a customer based on their date of birth.
• Measuring the duration of a project or event.
• Analyzing trends over specific time intervals.

Conclusion

Calculating the total number of days between two specific dates in SQL is a straightforward operation with the DATEDIFF() function. By using this function, we can perform date calculations efficiently, whether for tracking time intervals, analyzing historical data, or generating reports. Understanding how to use DATEDIFF() and its parameters enables us to handle various date-related queries with confidence. Practice these techniques, and we’ll find date calculations in SQL become second nature.

remmargorpp

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Article Tags :

• SQL
• Databases
• SQL-Query