Unclear problem in Chapter 3: Lab - Using $lookup


I just solved this problem. I was fooled by the statement:

Boeing 747 or an Airbus A380 (abbreviated 747 and 380 in air_routes)

I understood that to mean airplane would be either ‘747’ or ‘380’. This is false.

It would be helpful to state in the problem text that airplane might contain a list of types, e.g. ‘747 320 773’.

Thanks for a great course.



Hi @Nikolaj_Lundsgaard,

Thanks for sharing this feedback.

I will check with the team and get the lab statement updated.


I got trapped in this one too, due to this flight list problem, it would be nice upgrade the exercise description. thanks @Nikolaj_Lundsgaard!!

Also, I believe there is some mismatch in the results.

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I did not manage to make same results the official answer has. Maybe I am connected to another server, or smth. Did lookup from both sides with pipelines inside the join and got same answer of mine, but the numbers differ o_O

Hi @Dima_Chernin,

Please elaborate the issue that you are having.

Kind Regards,

@Sonali_Mamgain, I’ve found the problem already. The matter is airplane is not a single 747 or 380.
It could be “747 380”. What I used was $in operator, but should have used a regex /747|380/ .
@Nikolaj_Lundsgaard wrote this, but I was too in a hurry to read it carefully :slight_smile:

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