How can I create such a query in MS access so that only customers with more than 3 bookings show up?
SELECT Customers.Customer_ID
FROM Customers
INNER JOIN Bookings 
    ON Customers.Customer_ID = Bookings.Customer_ID
GROUP BY Customers.Customer_ID
HAVING COUNT(Customers.Customer_ID) &gt; 3


Visually (some terms are approximate because I have no MS Access with English interface):


Add both tables to Query pane
Join them by proper fields
Select fields from Customers table which you want to output, do NOT add fields from Booking table
Press Totals knob on the ribbon
Add one more Customers.Customer_ID to the fields list
Change its Grouping function from Grouping by to Count
Set the criteria for this field to >3
Uncheck Show if you do not need in its value