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Managing dates in any programming language can be a complex task and SQL is no exception. One frequent requirement in data analytics is to calculate the difference between two dates. Fortunately, SQL provides robust functions to work with dates. In this blog post, we will explore how to calculate the difference between two dates in SQL.
Using DATEDIFF function
In SQL, the DATEDIFF() function is used to get the difference between two dates. It provides the difference in terms of the unit specified like day, month, year, etc. The syntax for the DATEDIFF function is DATEDIFF(Unit, Initial_date, Final_date).
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SELECT DATEDIFF(DAY, '2020-01-01', '2020-12-31') AS DateDiff; |
In the above example, ‘DAY’ specifies the unit in which we want the result, which is the difference between the two dates: ‘2020-01-01’ and ‘2020-12-31’. The result would be 364, which represents the total number of days between these two dates.
Dealing with Time full timestamp
If you want to calculate the difference between two full timestamps (i.e., including time), you can do that too! You just need to specify the date and time in your parameters, and choose a smaller unit like hour, minute, or second. Let’s look at an example:
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SELECT DATEDIFF(SECOND, '2022-01-01 12:01:00', '2022-01-01 13:00:00') as DateDiff; |
In this case, we are calculating the difference in seconds. The first timestamp is ‘2022-01-01 12:01:00’ and the second timestamp is ‘2022-01-01 13:00:00’. The result of this calculation would be 3540 seconds.
Note:
While DATEDIFF function is effective, one need to keep in mind that it only provides the difference of the unit specified. Therefore, if ‘YEAR’ is specified, for instance, it ignores the day and month portions of the date expressions.
Wrapping Up
Dates can be tricky to work with in SQL, but with the right functions, you can do a lot. The DATEDIFF() function is a powerful tool for calculating the difference between dates, and it’s very flexible with what unit of time you want to use.
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