Big SQL Energy Beginner Course: Lesson 20 Date_Add()

Jan 20, 2025

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Lesson 20: Date_Add()

🎥 Video

Date_Add() is really useful for manipulating dates and creating new dates from ones you already have. What if you want to create an estimated delivery date based on the original order date? Or if you want to come up with a date to follow up with customers after their orders for reviews? Here’s the basic syntax and an example of how to use date_add:

date_add(date, interval interval_value interval_unit)

date_add(order_date, interval 7 day)

Note that there are different syntaxes for date_add(), so the ordering of the arguments may vary across platforms and dialects. Google or ChatGPT if you have syntax issues!

We can use date_add() to create an estimated delivery date that’s 7 days after each order’s order date:

SELECT
  order_id,
  order_date,
  date_add(order_date, interval 7 day) as estimated_delivery_date
FROM
  customer_orders_with_coupon;

Notice that we can also do different time units as well. For example, we can create a new date 3 months after the order date to follow up with customers for a review. We can even convert the output to a true date using cast (or double colons like :: ) if the output appears with a blank timestamp:

select 
    order_id,
    customer_id,
    order_date,
    DATE_ADD(order_date, interval 3 month)::date AS follow_up_date
FROM 
    orders

Of course we can also use date_add() calculations to filter an output or result set as well. Below, we’re filtering for only orders that have a follow up date in the upcoming week based on the currentdate (which we learned in a past lesson!).

select 
    order_id,
    customer_id,
    order_date,
    DATE_ADD(order_date, interval 3 month)::date AS follow_up_date
FROM 
    orders
WHERE
   follow_up_date between current_date() and date_add(current_date(), interval 7 day)

Of course, this output of this is null with our sample dataset since we don’t have live, recent data, but you can see how this is a useful functionality when it comes to weekly reporting. Imagine having this dynamic date filter for a query you need to update and pull once a week! It would be way better than hardcoding the date and manually updating it each time.

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