Apr 09

MongoDB: Array Operations

Try these Array Operations:

db.posts.find({}, {_id:0, category:1, tags:1});
db.posts.updateMany({category:'Event'}, {$addToSet:{tags:"Tech"}});
db.posts.updateMany({category:'Event'}, {$push:{tags:"Tech Event"}});
db.posts.updateMany({category:'Event'}, {$pull:{tags:"Tech"}});
db.posts.updateOne( { likes: 4 }, { $pop: { tags: -1 } } )
db.posts.updateMany({}, {$pull:{tags:["Tech"]}});
 db.posts.updateMany({}, {$pull:{tags:"Tech"}});
db.posts.updateMany({}, {$pull:{tags:{$in:["Tech", "Tech Event"]}}});
Run it several times: db.posts.updateMany({}, {$push:{tags:"Tech Event"}});
Check data: db.posts.find({}, {tags:1, _id:0});
Pull and then check data: 
db.posts.updateMany({}, {$pull:{tags:{$in:["Tech", "Tech Event"]}}});
db.posts.find({}, {tags:1, _id:0});

Use data from the URL below: https://www.w3schools.com/mongodb/mongodb_mongosh_insert.php

db.posts.insertMany([  
  {
    title: "Post Title 2",
    body: "Body of post.",
    category: "Event",
    likes: 2,
    tags: ["news", "events"],
    date: Date()
  },
  {
    title: "Post Title 3",
    body: "Body of post.",
    category: "Technology",
    likes: 3,
    tags: ["news", "events"],
    date: Date()
  },
  {
    title: "Post Title 4",
    body: "Body of post.",
    category: "Event",
    likes: 4,
    tags: ["news", "events"],
    date: Date()
  }
])

Theory/Concept: