Summary of commonly used sentences in MongoDB

preface

MongoDB and MySQL basic statements are still very different, today I will introduce some of the commonly used basic statements of MongoDB, the following words do not say much, let's take a look at the detailed introduction

MONgoDB delete statement

delete() Delete

Delete a collection

db.collection.deleteOne()

Delete multiple collections

db.collection.deletMany();

remove() Delete

Delete all name: Li Si's data

db.student.remove({name:"Li Si"});

Delete only one sex: male data delete only one

db.student.remove({sex:"male"},true);

delete all

db.student.remove({});

false deletion of database

Sometimes when the user deletes the operation, the requirement is that only the data is hidden, not really deleted from the database.

At this time, fake deletion was used. For example, this is Zhang Sanfa's two Weibo posts:

db.student.insert([ {name:"Zhang San",content:"Good mood today",isDel:0}, {name:"Zhang San",content:"Average mood today",isDel:0},]);

The user adds two pieces of data, but only keeps the latter one. Delete the former one. In this case, use false deletion. Add a field isDel:0 when adding data.

So when the user deletes data, it executes not the remove method, but the update method.

db.student.update({"_id" : ObjectId("5bd6a46f1eb7a22fa07cb382")},{ $set:{ isDel:1 }});

When isDel:0 is indicating that the user has not deleted, 1 is indicating that the user has deleted.

Therefore, when querying, you need to filter the name and isDel conditions

db.student.find({name:"Zhang San",isDel:0});

Query the data that the user has not deleted:

Then you can fake deletion.

Operation and modification of batch data

Insert 10000 documents into the collection

var arr= [];for(var i=0;i