Summary of common MongoDB commands

Simply add, delete, change and check the data

Specify whether to display or not to display a field in the query result

For example, we want to find all the data in the lessons collection, but we don't want to include the slides field in the return result; Because slides is a huge array of images in base64, it affects the reading of the query results.
So we can follow query object with one parameter. As follows:

db.lessons.find({}, {slides:0});

You can also specify which fields to display:

db.bios.find(

{ },

{ name: 1, contribs: 1, _id: 0 }

)

The comparison operation is larger than and smaller than

We want to query the data records between startTime and endTime, and we want Content to contain the Numbers 1 to 5.

db.wemessages.find( {$and: [

    { CreateTime: {$gt: (startTime.getTime()/1000).toString()} },

    { CreateTime: {$lt: (endTime.getTime()/1000).toString()} },

    { Content: {$in: ['1','2','3','4','5']} }

  ]}

);

Here we use the $and logical operator, and the $gt, $lt, $in comparison operators.

About MongoDB operator, see: http: / / docs mongodb. org/manual/reference/operator/query /

Updates some properties of a record

Using $set means updating only the specified field without modifying the other fields, which is our general intent.

db.lessons.update({}, {$set:{'course_id':'c.101'}});

Update multiple records

Use {multi: true}

db.lessons.update({}, {$set:{'course_id':'c.101'}}, {multi: true});

db.muusers.update({username: 'tom'}, {$set: {mobile: '6508639713'}}, {multi: true});

Sort query results

Use the sort method

db.muusers.find().sort({firsttime: -1});

Minus 1 descending, 1 ascending

View the query results cleanly

Use the pretty method

db.lessons.find({lesson: 1}, {slides: 0, mp3voice:0, wavvoice:0, wavvoicemin: 0}).pretty();

View a record that does not have a field

Using the $exists

db.questions.find({'sequence_id': 1, 'pngslide': {$exists: false}});

db.mycollection.find( { "price" : { "$exists" : false } } )

Limit the number of query results limit and how many records skip is skipped to begin with

Use limit and skip

db.translation_memory.find({mp3voice: {$exists: false}}, null, {limit: 100});

Delete everything in collection

Use the remove method of collection

db.collection.remove();

Get the length of one field in collection

Chain calls

db.lessons.find({lesson: 1}).toArray()[0].slides.join('').length

Collection operation

Renamed collection

Use the renameCollection method

db.quizzes.renameCollection('questions');

Delete 1 field

Using the $unset

db.questions.update({}, {$unset: {quiz_name:1}}, {multi: true});

db.learning_progress.update({}, {$unset: {lesson:1}}, {multi: true});

db.lessons.update({}, {$unset: {wavvoice:1, wavvoicemin:1}}, {multi: true});

Modify the name of a field

Using the $rename

db.students.update( { _id: 1 }, { $rename: { 'nickname': 'alias', 'cell': 'mobile' } } )

Note: some keywords of MongoDB cannot be used as the name of Collection, for example: group.

That's all for this article, I hope you enjoy it.