$and operator
-------------

Find movies with high IMDb score and high Tomato meter value.

    db.movieDetails.find({$and: [
        {"imdb.rating": {$gte: 8.8}},
        {"tomato.meter": {$gte: 95}}
    ]})


How many movies did you find?

    TODO...


However, in this case $and is not necessary. We can write it in a simpler way:

    db.movieDetails.find({"imdb.rating": {$gte: 8.8}, "tomato.meter": {$gte: 95}})


But why do we need an $and operator then?

    db.movieDetails.find({"title": {$gt: "C"}, "title": {$regex: "a"}}, {_id: 0, title: 1}).pretty()

    If we write this, the second criterion will overwrite the first one! It will simply
    mean: find movies whose title contains the character "a".
    Why? We use the same key ("title") twice in a JSON document. Keys must be unique.


    Solution #1: use $and

    db.movieDetails.find({$and: [
        {"title": {$gt: "C"}},
        {"title": {$regex: "a"}}
    ]}, {_id: 0, title: 1})


    Solution #2: multiple criteria about a field

    db.movieDetails.find({"title": {$gt: "C", $regex: "a"}}, {_id: 0, title: 1}).pretty()

    Now the two criteria ($gt and $regex) are about the "title" field.