misc/mongodb.md
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## Intro - Collections are analogus to tables in relational databases - A collection consists of documents. Documents are analogus to a record. - A document is just a simple JSON object, or in mongodb's lingo, it's a BSON object. - The schema of each document in a collection is not strict my default. i.e A collection can have documents that are completely different from each other. - an `_id` field is like the primary key of a document. If one is not provided while inserting a new document, then mongodb creates on of the type `ObjectId` ## Simple Operations ### Show All Databases ``` show dbs ``` ### Show Current Database ``` db ``` ### Create Or Switch Database ``` use acme ``` ### Drop ``` db.dropDatabase() ``` ### Create Collection ``` db.createCollection('posts') ``` ### Show Collections ``` show collections ``` ### Insert Row ``` db.posts.insert({ title: 'Post One', body: 'Body of post one', category: 'News', tags: ['news', 'events'], user: { name: 'John Doe', status: 'author' }, date: Date() }) ``` ### Insert Multiple Rows ``` db.posts.insertMany([ { title: 'Post Two', body: 'Body of post two', category: 'Technology', date: Date() }, { title: 'Post Three', body: 'Body of post three', category: 'News', date: Date() }, { title: 'Post Four', body: 'Body of post three', category: 'Entertainment', date: Date() } ]) ``` ### Get All Rows ``` db.posts.find() ``` ### Get All Rows Formatted ``` db.find().pretty() ``` ### Find Rows ``` db.posts.find({ category: 'News' }) ``` ### Sort Rows ``` # asc db.posts.find().sort({ title: 1 }).pretty() # desc db.posts.find().sort({ title: -1 }).pretty() ``` ### Count Rows ``` db.posts.find().count() db.posts.find({ category: 'news' }).count() ``` ### Limit Rows ``` db.posts.find().limit(2).pretty() ``` ### Chaining ``` db.posts.find().limit(2).sort({ title: 1 }).pretty() ``` ### Foreach ``` db.posts.find().forEach(function(doc) { print("Blog Post: " + doc.title) }) ``` ### Find One Row/Document ``` db.posts.findOne({ category: 'News' }) ``` ### Find Specific Fields ``` db.posts.find({ title: 'Post One' }, { title: 1, author: 1 }) ``` ### Update a Document ``` db.posts.update({ title: 'Post Two' }, { title: 'Post Two', body: 'New body for post 2', date: Date() }, { upsert: true }) ``` The first argument to `update` specifies which document you are targeting to update. This should be the `_id` field to keep it unique. ### Update Specific Field ``` db.posts.update({ title: 'Post Two' }, { $set: { body: 'Body for post 2', category: 'Technology' } }) ``` If the field does not exist then it is added. ### Add an element to an array ``` db.test.update( { _id : 133 }, { $push : { <field1>: <value1>} } ) ``` field1 is an array and <value1> is the elemnet/document will be inserted into that array. ### Increment Field (\$inc) ``` db.posts.update({ title: 'Post Two' }, { $inc: { likes: 5 } }) ``` ## Rename Field ``` db.posts.update({ title: 'Post Two' }, { $rename: { likes: 'views' } }) ``` ## Delete Row ``` db.posts.remove({ title: 'Post Four' }) ``` ## Sub-Documents ``` db.posts.update({ title: 'Post One' }, { $set: { comments: [ { body: 'Comment One', user: 'Mary Williams', date: Date() }, { body: 'Comment Two', user: 'Harry White', date: Date() } ] } }) ``` ## Find By Element in Array (\$elemMatch) ``` db.posts.find({ comments: { $elemMatch: { user: 'Mary Williams' } } } ) ``` ## Add Index ``` db.posts.createIndex({ title: 'text' }) ``` ## Text Search ``` db.posts.find({ $text: { $search: "\"Post O\"" } }) ``` ## Greater & Less Than ``` db.posts.find({ views: { $gt: 2 } }) db.posts.find({ views: { $gte: 7 } }) db.posts.find({ views: { $lt: 7 } }) db.posts.find({ views: { $lte: 7 } }) ```