mongo-exercises.md

• How many zips in the sample_training.zips dataset are neither over-populated nor under-populated? In this case, we consider population of more than 1,000,000 to be over- populated and less than 5,000 to be under-populated.

db.zips.find({
              $nor: [
                { pop: { $gt": 1000000 } },
                { pop: { $lt: 5000 } }
              ]
            }).count()

• How many companies in the sample_training.companies dataset were either founded in 2004, or in the month of October and either have the social category_code or web category_code?

db.companies.find({
    $and: [
        {
            $or: [{founded_year: 2004}, {founded_month: 10}]
        },
        {
            $or: [{category_code: "web"}, {category_code: "social"}]
        }
    ]
}).count()

• How many companies in the sample_training.companies collection have the same permalink as their twitter_username?

db.companies.find({ 
    $expr:  { $eq: ["$permalink", "$twitter_username"] }
}).count()

• What is the name of the listing in the sample_airbnb.listingsAndReviews dataset that accommodates more than 6 people and has exactly 50 reviews?

?

Hey please check fork for What is the name of the listing in the sample_airbnb.listingsAndReviews dataset that accommodates more than 6 people and has exactly 50 reviews?

db.listingsAndReviews.find({ "reviews": { "$size":50 },
"accommodates": { "$gt":6 }})

db.listingsAndReviews.find({
    "property_type": "House",
    "amenities": {
        "$all": ["Changing table"]
    }
}).count()

db.listingsAndReviews.find({
    "$and": [{
        "property_type": "House"
    }, {
        "amenities": {
            "$all": ["Changing table"]
        }
    }]
}).count()

Hi everyone!
I have a question about chapter 4 lecture 6 lab. 2: "How many inspections from the sample_training.inspections collection were conducted in the city of NEW YORK?"
My query: db.inspections.find({"address.city":"New York"}).count()
Result: 5

But it's not correct... Can anyone explain to me why ?

SOLVED: it's "NEW YORK"

Hi everyone!
I have a question about chapter 4 lecture 6 lab. 2: "How many inspections from the sample_training.inspections collection were conducted in the city of NEW YORK?"
My query: db.inspections.find({"address.city":"New York"}).count()
Result: 5

But it's not correct... Can anyone explain to me why ?

SOLVED: it's "NEW YORK"

I think you should write:
db.inspections.find({"address.city":"NEW YORK"}).count()

haha thanks for the help

How many companies in the sample_training.companies collection have the same permalink as their twitter_username?
db.companies.find({
$expr: { $eq: ["$permalink", "$twitter_username"] }
}).count()
after using this query it show the result 0

When i enter the same query in Atlas collections filter :
{"$expr":{"$eq":["$permalink","$twitter_username"]}}
It shows many results.
can someone help me with this issue

$expr:

"$expr":

we can check what collections we have by giving show dbs, after selecting any one database, how to navigate back to parent databases ?

In the first exercise, it's "$gt" : 5000, and "$lt": 100000

we can check what collections we have by giving show dbs, after selecting any one database, how to navigate back to parent databases ?

use database_name

In the first exercise, it's "$gt" : 5000, and "$lt": 100000

i guess it should be $gte and $lte