SQL DATEDIFF Function
Quick summary: The SQL DATEDIFF() function returns the number of days between two dates.
SQL DATEDIFF Syntax
date1 - date2SQL
SQL DATEDIFF Basic examples
SELECT DATEDIFF('2026-02-10', '2026-02-01');SQL
Output:
9Calculates the difference in days.
SQL DATEDIFF Real-world usage
SELECT DATEDIFF(NOW(), created_at) FROM users;SQL
Output:
Account age in daysMeasures time since creation.
SQL DATEDIFF Edge cases
SELECT DATEDIFF('2026-02-01', '2026-02-10');SQL
Output:
-9Negative values indicate reversed order.
SQL DATEDIFF Common mistakes
Assuming DATEDIFF includes time
DATEDIFF ignores time portions.
Incorrect
DATEDIFF(NOW(), created_at)Correct
TIMESTAMPDIFF(HOUR, created_at, NOW())Use TIMESTAMPDIFF for time precision.
SQL DATEDIFF Frequently Asked Questions
What does DATEDIFF() do in SQL?
Returns the difference between two dates.
Use case of DATEDIFF()?
Calculating date intervals.
Syntax?
DATEDIFF(date1, date2).
Return type?
Integer.
Common mistake?
Wrong parameter order.
Units?
Days (usually).
Handles NULL?
Returns NULL.
Alternative?
TIMESTAMPDIFF.
Used in WHERE?
Yes.
Supports time?
Depends on DB.
Performance?
Fast.
Best practice?
Be explicit with date order.