Last active
August 29, 2015 14:15
-
-
Save ingumsky/a1457a9e09cfd8967e7c to your computer and use it in GitHub Desktop.
M101js (MongoDB course for javascript developers)
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
/* | |
You'd better find solutions for those assesments yourself to be sure | |
you understand MongoDB Aggregation Framework properly. | |
But if you stuck and need some help and clues to guide you | |
feel free to use the commands below as a reference. | |
Note that I splitted each and every aggregation stage. | |
Hopefully it will help you to find why your code is not working as you want. | |
*/ | |
// hw 5.1 | |
db.posts.aggregate([ | |
{"$unwind": "$comments"}, | |
{"$group": { "_id": "$comments.author", "posts": { $sum: 1 } }}, | |
{"$project": {"_id": 0, "author": "$_id", "posts": 1} }, | |
{"$sort": {"posts": 1}}, | |
]); | |
// hw 5.2 | |
db.zips.aggregate([ | |
{ | |
$project: { | |
city: 1, state: 1, pop: 1, zip: "$_id", _id: 0, | |
} | |
}, | |
{ | |
$group: { | |
"_id": { | |
city: "$city", state: "$state" | |
}, | |
zips: { | |
$addToSet: "$zip" | |
}, | |
pop: { | |
$sum: "$pop" | |
} | |
} | |
}, | |
{ | |
$match: { | |
pop: { | |
$gt: 25000 | |
}, | |
_id.state: { | |
$in: ['CT', 'NJ'] | |
} | |
} | |
}, | |
{ | |
$group: { | |
_id: null, | |
population: { | |
$avg: "$pop" | |
} | |
} | |
}, | |
]); | |
// hw 5.3 | |
db.grades.aggregate([ | |
{ | |
$unwind: "$scores" | |
}, | |
{ | |
$match: { | |
"scores.type": { | |
$in: ['exam', 'homework'] | |
} | |
} | |
}, | |
{ | |
$group: { | |
"_id": { | |
"class": "$class_id", | |
"student": "$student_id", | |
}, | |
"student_average": { | |
$avg: "$scores.score", | |
} | |
} | |
}, | |
{ | |
$group: { | |
"_id": "$_id.class", | |
"average": { | |
$avg: "$student_average", | |
} | |
} | |
}, | |
{ | |
$sort: { | |
"average": -1, | |
} | |
} | |
]); | |
// hw 5.4 | |
db.zips.aggregate([ | |
{ | |
$project: { | |
first_char: { | |
$substr: ["$city", 0, 1] | |
}, | |
pop: 1, | |
} | |
}, | |
{ | |
$match: { | |
first_char: { | |
$regex: "[0-9]" | |
} | |
} | |
}, | |
{ | |
$group: { | |
_id: null, | |
pop: { | |
$sum: "$pop" | |
} | |
} | |
} | |
]); |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment