├── .gitignore
├── group-sum.js
├── joins.js
├── unwind.js
├── basics.js
├── sort-skip-limit.js
└── readme.md


/.gitignore:
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1 | .idea
2 | .DS_Store
3 | 


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/group-sum.js:
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 1 | db.tweets.aggregate([
 2 |     {
 3 |         $group: {
 4 |             _id: "$user.screen_name",
 5 |             tweetCount: {
 6 |                 $sum: 1
 7 |             },
 8 |             favoriteCount: {
 9 |                 $sum: "$favorite_count"
10 |             }
11 |         }
12 |     },
13 |     {
14 |         $sort: {
15 |             tweetCount: 1
16 |         }
17 |     }
18 | ])
19 | 


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/joins.js:
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 1 | db.product.aggregate([
 2 |     {
 3 |         $lookup: {
 4 |             from: "category",
 5 |             localField: "categoryId",
 6 |             foreignField: "_id",
 7 |             as: "categoryDetail"
 8 |         }
 9 |     },
10 |     {
11 |         $project: {
12 |             "name": "$name",
13 |             "category": {
14 |                 $arrayElemAt: ["$categoryDetail", 0]
15 |             }
16 |         }
17 |     }
18 | ])
19 | 


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/unwind.js:
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 1 | db.tweets.aggregate([
 2 |   {
 3 |     $project: {
 4 |       'username': '$user.screen_name',
 5 |       'hashtags': '$entities.hashtags',
 6 |       'tweet': '$text'
 7 |     }
 8 |   },
 9 |   {
10 |     $unwind: '$hashtags'
11 |   },
12 |   {
13 |     $group: {
14 |       _id: '$hashtags.text',
15 |       count: {
16 |         $sum: 1
17 |       }
18 |     }
19 |   },
20 |   {
21 |     $sort: {
22 |       count: -1
23 |     }
24 |   },
25 |   {
26 |     $limit: 5
27 |   }
28 | ]);
29 | 


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/basics.js:
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 1 | db.tweets.aggregate([
 2 |   // Stage 1:
 3 |   // Accepts the query, similar to `find`
 4 |   {
 5 |     $match: {
 6 |       'user.verified': true
 7 |     }
 8 |   },
 9 |   // Stage 2:
10 |   // Extract the username and create dummy description
11 |   {
12 |     $project: {
13 |       // Here we are not renaming the field and getting it as it is
14 |       // "user.screen_name": 1,
15 |       'user_name': '$user.screen_name',
16 |       'description': {
17 |         '$concat': ['Find them @', '$user.screen_name']
18 |       }
19 |     }
20 |   }
21 | ]);


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/sort-skip-limit.js:
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 1 | db.tweets.aggregate([
 2 |   // Stage 1:
 3 |   // Get all the tweets which are not retweets from the verified users
 4 |   {
 5 |     $match: {
 6 |       "user.verified": true,
 7 |       "retweeted_status": null
 8 |     }
 9 |   },
10 |   // Stage 2:
11 |   // Sort them by the retweet count in each
12 |   {
13 |     $sort: {
14 |       "retweet_count": -1
15 |     }
16 |   },
17 |   // Stage 3, 4:
18 |   // Skip the top retweet and get the second most retweeted one
19 |   {
20 |     $skip: 1
21 |   },
22 |   {
23 |     $limit: 1
24 |   }
25 |   // Stage 5:
26 |   // Project to get only the relevant fields
27 |   {
28 |     $project: {
29 |       "tweet": "$text",
30 |       "username": "$user.screen_name",
31 |       "retweet_count": -1,
32 |     }
33 |   }
34 | ]);
35 | 


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/readme.md:
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 1 | ## egghead-mongo-aggregation
 2 | Codebase supporting my "Aggregation in MongoDB" lectures on egghead
 3 | 
 4 | ## Videos
 5 | * [Introduction and Basic Pipelines – `$match`, `$project`, `$concat`](https://egghead.io/lessons/egghead-find-and-manipulate-data-using-aggregation-in-mongodb)
 6 | * [Sort, Skip and Limit records in MongoDB aggregation – `$sort`, `$skip`, `$skip`](https://egghead.io/lessons/egghead-sort-skip-and-limit-records-in-mongodb-aggregation)
 7 | * [Writing Join Queries — `$lookup`, `$project`, `$arrayElemAt`](https://egghead.io/lessons/egghead-write-joins-in-mongodb)
 8 | * [Group by and Sum in MongoDB — `$group`, `$sum`, `$sort` operators](https://egghead.io/lessons/egghead-group-by-and-sum-in-mongodb)
 9 | * [Perform Group Operations on Array fields - `$unwind`, `$group`, `$sort`, `$limit`](https://egghead.io/lessons/egghead-perform-group-operations-on-array-fields-in-mongodb),
10 | * ...
11 | * [Suggest!](https://github.com/kamranahmedse/egghead-mongo-aggregation/issues/new)
12 | 


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