Using Oracle’s DATEDIFF Function to Compare Dates with Today’s Date

In this article, we will explore how to compare the LastUpdated column with today’s date in days using Oracle’s built-in functions.

Introduction to Oracle’s DATEDIFF Function

Oracle provides a function called DATEDIFF that can be used to calculate the difference between two dates. However, it is not directly applicable for comparing a column value with a specific date. In this section, we will discuss how to use the DATEDIFF function in conjunction with other Oracle functions to achieve our goal.

Understanding the DATEDIFF Function

The DATEDIFF function takes two arguments: the start date and the end date. It returns the difference between the two dates in a specified unit of time (e.g., days, months, years). Here’s an example:

SELECT DATEDIFF(DAY, '2022-01-01', '2022-12-31') AS "days_in_year"

In this case, DATEDIFF returns the number of days between January 1st and December 31st.

Truncating Off Time in Oracle

When working with dates in Oracle, it’s essential to consider time zones. To avoid issues due to different time zones, we can truncate off the time component from both the LastUpdated column and today’s date using the TRUNC function.

Using TRUNC to Truncate Dates

The TRUNC function truncates a date to a specified unit of time (e.g., day, month). Here’s an example:

SELECT TRUNC('2022-01-01 12:00:00') AS "truncated_date"

In this case, TRUNC returns ‘2022-01-01’.

Comparing LastUpdated with Today’s Date

Now that we have a way to truncate off the time component from both dates, let’s compare the LastUpdated column with today’s date. We’ll use the DATEDIFF function in conjunction with the TRUNC function to calculate the difference between the two dates.

Using DATEDIFF to Compare Dates

Here’s an example:

SELECT DISTINCT "AppName", "ApprovedForRelease",
       (TRUNC(SYSDATE) - TRUNC("LastUpdated"))  AS "DaySinceUpdated" 
FROM BR_APP
WHERE "ApprovedForRelease" = 'Y';

In this case, SYSDATE returns the current date and time. We use TRUNC to truncate off the time component from both dates before calculating the difference using DATEDIFF.

Why Doesn’t This Work?

Unfortunately, Oracle’s DATEDIFF function cannot be used directly with a column value as an argument. The error message you encountered in your original question (ORA-00904: "DATEDIFF": invalid identifier) is because DATEDIFF expects two date literals as arguments.

The code you provided:

SELECT DISTINCT "AppName", "ApprovedForRelease",
       DATEDIFF(DAY,"LastUpdated",GETDATE())  AS "DaySinceUpdated" 
FROM BR_APP
WHERE "ApprovedForRelease" = 'Y';

is based on SQL Server, which allows DATEDIFF to take a column value as an argument. However, Oracle’s implementation is different.

Conclusion

In conclusion, we’ve explored how to compare the LastUpdated column with today’s date using Oracle’s built-in functions. By truncating off the time component from both dates using the TRUNC function and then calculating the difference between the two truncated dates, we can achieve our goal.

Last modified on 2023-12-22