DateDiff in SQL: A Complete Guide in 2024

Introduction

DateDiff in SQL () is a function that compares two or more dates by returning the difference. This DateDiff function is used to measure the difference between two dates which can be in years, months, weeks, etc.

The function DateDiff in SQL may or may not return the original date. But, it would return the number of times a particular date crossed the defined date part boundaries between the start and the end date.

Now, let’s understand what a DateDiff SQL function is.

SELECT DATEDIFF(YEAR, '2019/10/05 12:20:23', '2021/10/05 13:23:47') AS [Years],
DATEDIFF(QUARTER, '2019/10/05 12:20:23', '2021/10/05 13:23:47') AS [Quarters],
DATEDIFF(MONTH, '2019/10/05 12:20:23', '2021/10/05 13:23:47') AS [Months],
DATEDIFF(WEEK, '2019/10/05 12:20:23', '2021/10/05 13:23:47') AS [Weeks],
DATEDIFF(DAY, '2019/10/05 12:20:23', '2021/10/05 13:23:47') AS [Days],
DATEDIFF(HOUR, '2019/10/05 12:20:23', '2021/10/05 13:23:47') AS [Hours],
DATEDIFF(MINUTE, '2019/10/05 12:20:23', '2021/10/05 13:23:47') AS [Minutes],
DATEDIFF(SECOND, '2019/10/05 12:20:23', '2021/10/05 13:23:47') AS [Seconds];

Results:

-- | Years | Quarters | Months | Weeks | Days | Hours | Minutes | Seconds |
-- |-------|----------|--------|-------|------|-------|---------|---------|
-- | 2 | 8 | 24 | 105 | 731 | 17545 | 1052703 | 63162204 |

What is a DateDiff SQL Function?

The DateDiff SQL is a powerful tool to calculate the difference between two dates. The tool is designed to work across different platforms, flexibility in handling date-related data.

Also, this tool measures time spans. It requires three parameters: the unit of measure for various intervals (such as days, months, or years) and two dates for which you want to calculate the difference.

Moreover, the DateDiff SQL function is broadly supported across various database systems, making it a standard choice for sql DateDiff day calculations. This tool is also compatible with systems like Azure SQL and Analytics Platform System. They start from versions as early as a SQL server 2008.

The DateDiff function () is mainly used within a data manipulation function. It also can break down time intervals into specific units. This makes it inevitable for the tasks that require a detailed time-based analysis or reporting where understanding the duration between two dates becomes quite important.

Now, let’s understand the features of the function DateDiff() in SQL Server

Features of DateDiff () Functions in SQL Server

● The DateDiff () function is used to find the differences between two specified dates or times.

● The function comes under Data functions.

● Moreover, the DateDiff function () includes the time interval section and also the date value section.

Now, let’s understand the four main applications of DateDiff () between two specified values of the data.

Three Main Applications of DateDiff () Functions in SQL Server

● Date interval Calculation: The determined date parts between two dates are figured out using this function.

● Date Part Flexibility: Year, months, days, etc are a part of the Date part.

● Versatility in Date Comparisons: This function enables you to compare dates from multiple time frames, which makes the trend analysis possible.

Now, let’s understand Syntax of DateDiff function in SQL

Syntax of DateDiff

The DateDiff () function compares two individual dates and returns the difference. This function is specifically used to measure the difference between two dates in years, months, weeks, etc.

Moreover, this function might or might not return the original date. But, it would return the number of times it crosses the defined date part between the start and the end dates.

So, what is its Syntax?
Let’s understand it

The syntax of DateDiff goes as under:

DateDiff (date_part,start_date_value1, end_date_value2)

In the above syntax, Date_part is nothing but a month, year, or day. In the above formal difference, you can find that result. start_date_value1 is the value of the starting date and the end_date_value2 is the value of an ending date.

Are you ready to understand the Code?

Code:

Select DateDiff (month,’2011-03-07’ , ‘2021-06-24’)

In the example, you can see the number of months between the start date and the end date. From the inputs you got there are 123 months between the dates 07/03/2011 and 24/3/2011.

In addition, you can also find the number of hours, minutes, seconds, and so on in terms of details between two dates, with the help of DateDiff parameter.

There are a number of arguments associated with the DateDiff function of SQL. They are mentioned below:

DateDiff () Arguments:

The date part is the portion of the date by which you can compare the end date and start date, like a year, a fifth, a month, or a week. In the below table, you can find the valid date bits.

The dates that you need to compare are the start date and end date. Moreover, this needs to be converted to DATE, DATETIME, DATETIMEOFFSET, DATETIME2, SMALLATETIME, or TIME values.

Now, let’s understand the three arguments in the DateDiff () function in SQL.

● DATEPART

● Starting Date

● Ending Date

Starting Date/Ending Date:

The starting Date and ending Date are similar to follow the format to indicate the values. For example, the date should be as YYYY-MM-DD Sec:Min:Hour.

The format of these may be

● time

● Date

● Datetime

● Datetime2

● Datetimeoffset

● Smalldatetime

DATE PART in Argument:

The main argument in the DateDiff function is concerning DATEPART:

The DateDiff () function returns an integer value which will represent the difference between the start date and an end date, with the date part being the unit. If the result is out of range for the integer the DateDiff () function returns an error. Here, the DateDIff Big () function can be used instead.
Now, let’s understand the Return Type of DateDiff ()

What is the Return Type in DateDiff ():

A Date Difference SQL server would return as an integer representing the difference between two dates, i.e. date1 and date2 by specifying the unit as an interval.
If the output result is out of range for 32-bit integer (-2,147,483,648 to 2,147,483,647), then the DateDiff in an SQL Server returns an error. In the above case, one should leverage the DateDiff_Big() function.

Moving forward let’s understand a few examples of DateDiff SQL

Example 1: Calculate the number of days it takes to get the order delivered, from the order date to the delivery date.

SELECT
order_id,
DATEDIFF(day, order_date, delivery_date) AS delivery_days
FROM
Orders;

Example 2: Identify and determine the tenure of the employee in years based on their START date to their Current date

SELECT
employee_id,
DATEDIFF(year, start_date, CURRENT_DATE) AS years_of_service
FROM
employees;

Example 3: Identify and determine the tenure of the employee in years based on their START date to their Current date.

SELECT
YEAR(sale_date) AS sale_year,
MONTH(sale_date) AS sale_month,
sales_amount,
LAG(sales_amount) OVER (ORDER BY YEAR(sale_date), MONTH(sale_date)) AS previous_month_sales,
(sales_amount - LAG(sales_amount) OVER (ORDER BY YEAR(sale_date), MONTH(sale_date))) AS growth
FROM
sales;

Example 4: Further Identify and determine the tenure of the employee based on the years of their START date to their Current date.

SELECT
ticket_id,
opened_date,
DATEDIFF(day, opened_date, CURRENT_DATE) AS days_open
FROM
support_tickets
WHERE
status <> 'Resolved';
_________________
CREATE TABLE IF NOT EXISTS support_tickets (
ticket_id INT,
opened_date DATE,
status VARCHAR(20)
);
INSERT INTO support_tickets (ticket_id, opened_date, status) VALUES
(1, '2023-05-15', 'Open'),
(2, '2022-10-20', 'Open'),
(3, '2024-01-10', 'Pending'),
(4, '2021-08-30', 'Open'),
(5, '2023-11-05', 'Resolved');

Now, let’s modify the query to include the tenure calculation

SELECT
ticket_id,
opened_date,
DATEDIFF(CURRENT_DATE, opened_date) AS days_open,
CONCAT(
FLOOR(DATEDIFF(CURRENT_DATE, opened_date) / 365), ' years ',
FLOOR(MOD(DATEDIFF(CURRENT_DATE, opened_date), 365) / 30), ' months ',
MOD(MOD(DATEDIFF(CURRENT_DATE, opened_date), 365), 30), ' days'
) AS tenure
FROM
support_tickets
WHERE
status <> 'Resolved';

Now let’s understand the Considerations in DateDiff

What are the Considerations in a DateDiff?

Despite DateDiff being a remarkable tool, there are a few considerations to be kept in mind. Some of them are detailed below:

1. Data Type: It is important to ensure that the dates you’re comparing are in a proper format and are compatible with the DateDiff to avoid any error results.

2. Boundary Cases: Be cautious about scenarios like leap years or daylight saving time changes and, it can impact date calculations. Lastly, test your queries to detect any errors.

3. Time Component: Moreover, remember that DateDiff would solely consider the date part of your dates, disregarding the time component. Also, it allows you to adjust your approach accordingly if time precision is required.

4. Performance: While handling substantial data or queries by utilizing DateDiff might lead you to a slightly slowdown in the performance. By monitoring query execution times and optimizing as needed for efficiency.

Now, let’s move ahead and understand the advanced usage of the DateDiff SQL.

What are the Advanced Usages of DateDiff SQL?

The advanced usage of DateDiff SQL extends beyond the basic date calculations. The advanced usages include the following:

1. Dynamic Date Ranges: By employing DateDiff you can establish dynamic date ranges by enabling you to fetch data for the past 30 days or the ongoing quarter.

2. Age Calculation: Determining an individual’s age by comparing the birth date with the current date, thus leveraging the prowess of DataDiff.

3. Interval Analysis: Use the DateDiff for an in-depth interval analysis, such as identifying gaps or overlaps in the timestamps for date ranges.

4. A Conditional Logic: By using DateDiff along with the if-then logic you can do things based on how far apart dates are, like marking records with a special flag.

Conclusion

In simple words, DateDiff in SQL is like a magic wand that handles dates. Whether you’re figuring out time differences, analyzing the patterns, or setting up date ranges that change over time, DateDiff is here to help.

After understanding how it works and what to watch, you’ll be able to uncover all sorts of interesting information hidden in your data. So embrace DateDiff’s power by exploring and discovering the hidden secrets of time.

FAQs

1. How to calculate the difference between two dates in any SQL?

In order to calculate the difference between two dates use the DateDiff function.

2. What are the three arguments in any DateDiff in an SQL query?

The three major arguments for a DateDiff query are:

· Datepart unit

· Start date

· End date

3. How can you convert a DateDiff into a date?

You can convert a DateDiff into a date by adding results to a specific date using the DateAdd function.

4. What is the formula for DateDiff

The formula or syntax for DateDiff is DateDiff(end_date, Start_date)

5. How can you use DateDiff in MYSQL?

The formula for DateDiff in MySQL would be similar to SQL.

6. How to subtract one day from a date in SQL?

By subtracting one day from a date in SQL, use DATEADD with a negative value for the day's argument.