Question

I have 2 tables: Product, User.

Product:
    Date(Datetime)
    Phone_Number(Number).

User: 
    Date (Datetime)
    Phone_Number(Number)
    Type(Value of N or C).

When a new user is added to the User table, it is given a date, Phone Number and value of “N” (N for New).
When a user gets cancelled, it is given a date, the Phone Number and value of “C” (C for Cancelled).

Using MySQL, I need to find out the date difference between the Date the user was created and the date the user was cancelled and if they had a product (can match the user to the product by Phone Number) between the date of the creation and the date of the cancellation.

Any assistance would be greatly appreciated as my Query writing isn’t terrible but this I can’t work out.

Thanks.

Answer 1

You need to start by self-joining the User table to find the created and cancelled dates. Then join to the Product table to see if anything is there.

SELECT u.Phone_Number, u.Created, u.Cancelled, p.Date as 'ProductDate'
FROM (
    SELECT u1.Phone_Number, u1.Date as 'Created', u2.Date as 'Cancelled'
    FROM User u1
      JOIN User u2 on u1.Phone_Number=u2.Phone_Number
    WHERE u1.Type = 'N'
      and u2.Type = 'C'
  ) u
  LEFT JOIN Product p on u.Phone_Number = p.Phone_Number
                     and p.Date between u.Created and u.Cancelled