Beginner

220. Date Difference

Learn how to calculate the difference between two dates.

📘 Lesson 220 of 728 ⏱ 9 min 🎯 Intermediate

Date-difference calculations determine the amount of time between two date or timestamp values. The exact function and unit depend on the database system.

Calculating date differences is essential for measuring durations, aging, turnaround times, and business performance.

Calculate how many days an order took to complete.

SQL 
SELECT
    OrderID,
    OrderDate,
    DeliveryDate,
    DeliveryDate - OrderDate AS DeliveryDays
FROM Orders;

Date differences are widely used for SLA monitoring, employee tenure, invoice aging, order processing, customer response time, and operational analysis.

  • Date difference measures elapsed time.
  • The result can be expressed in different units.
  • Syntax varies across database systems.
  • It is useful for SLA analysis.
  • It is commonly used in aging calculations.
What is date difference used for?

It is used to calculate the elapsed time between two dates or timestamps.

Where is date difference useful for a Data Analyst?

It is useful for SLA measurement, aging analysis, turnaround time, customer response time, and operational reporting.

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