Mongodb Study Notes 02 and mongodb Study Notes

Mongodb Study Notes 02 and mongodb Study Notes
Mongodb Study Notes 02-CURD operations

CURD indicates Create, Update, Read, and Delete operations.

Create a database
Directly use the database name and create a collection to create a database.

Create collecion

db.createCollection("collectionName")  

Create collection implicitly

 db.collectionName.insert({xxxxxx})  

Delete collection

db.collectionName.drop()  

Delete Database

db.dropDatabase()

Insert data

db.collectionName.insert({xxxxxx})  

The "_ id" field is automatically added by default. If you do not want to automatically add it, you can specify the value of the "_ id" field in the inserted data.
Multiple data records can be inserted at a time.

db.collectionName.insert(( {xxx },{xxx },{xxx }))  

Delete data

Db. collectionName. remote (query expression, option)

Option: {JustOne: true/false} default value: false

Db. stu. remove () delete all content in the stu document
Db. stu. remove ({name: 'billvsme '}) deletes all information named "billvsme" in the stu document.
Db. stu. remove ({name: 'billvsme '}, true) plus true, indicating that onlyOne row

Search for Data

Db. stu. find (query expression, query column)

Db. stu. find () displays all data in the stu document
Db. stu. find ({name: 'billvsme '}) displays information with the name "billvsme" in the stu document.
Db. stu. find ({},{ name: true}) display name Columns

Update Data

Db. collectionName. update (query expression, new value, option)

Option: {Upsert: true/false, multi: true/false}
Upsert: If this parameter is set to true, a new value is inserted when the query does not exist. The default value is false.
Multi: if it is true, it indicates multiple matches. The default value is false.

Db. stu. update ({name: 'billvsme '}, {name: 'zhengkai', age: '22'}) matched with 'billvsme'OneInformation, and then change it to {name: 'zhengkai', age: '22'} (note that the original content will be deleted, replaced, rather than modified)

Update certain items in Data
Db. stu. update ({name: 'billvsme '}, {$ set: {age: 23}) matches 'billvsme'OneInformation, and then change its age to 23
$ Set is used here.
There are also similar:

• $ Inc increases db. stu. update ({name: 'billvsme '}, {$ inc: {age: 2}) by 2
• $ Rename: rename db. stu. update ({name: 'billvsme '}, {$ rename: {name: "username"}) to rename the name field to username
• $ SetOnInsert: When upsert is enabled, set the field value.
• $ Unset Delete specified column db. stu. update ({name: 'billvsme '}, {$ unset: {age: 1}) Delete the age Field