A developer needs to find all subscribers on the Customers data extension who made a...

To find all subscribers who made a purchase in the last 30 days, an INNER JOIN should be used to join the Customers data extension with the Orders data extension on the ContactKey. This ensures that only subscribers with matching records in both data extensions are retrieved.

SQL Query Example:

SELECT c.ContactKey FROM Customers c INNER JOIN Orders o ON c.ContactKey = o.ContactKey WHERE o.PurchaseDate >= DATEADD(day, -30, GETDATE())

Salesforce SQL JOINs