MongoDB Learning Note--curd operation

MongoDB Learning Notes 02–curd operations

Curd represents create (create), update, read (read), and delete operations

Create a library
You can create a library by directly use the library name and then create collection

Create Collecion

db.createCollection("collectionName")  

implicitly creating Collection

 db.collectionName.insert({xxxxxx})  

Delete Collection

db.collectionName.drop()  

Deleting a database

db.dropDatabase()

Inserting data

db.collectionName.insert({xxxxxx})  

The default is automatically added to the "_id" field, and if you don't want to automatically, you can specify the value of the "_id" field in the Insert data yourself
Multiple data can be inserted at one time

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

Delete data

db.collectionName.remote(查询表达式，选项)

option : {justone:true/false} default False

Db.stu.remove () Delete all the contents of the Stu document
Db.stu.remove ({name: ' billvsme '}) delete the information for name "Billvsme" under Stu document
Db.stu.remove ({name: ' Billvsme '}, True) plus true, indicating that only one row is deleted

Find data

db.stu.find(查询表达式，查询列)

Db.stu.find () Displays all data under the Stu document
Db.stu.find ({name: ' billvsme ') displays information for name "Billvsme" under Stu document
Db.stu.find ({},{name:true}) displays the Name column

Update data

db.collectionName.update(查询表达式，新值，选项)

option : {upsert:true/false,multi:true/false}
Upsert: If True, inserts a new value when the query does not exist and defaults to False
Multi: True to indicate that there is more than one match, the default is False

Db.stu.update ({name: ' billvsme '},{name: ' Zhengkai ', Age: ' 22 ') matches a message of name= ' Billvsme ' and then changes to {name: ' Zhengkai ', Age: ' 22 '} (note that the original content will be deleted, replaced, not modified)

update some items in the data
Db.stu.update ({name: ' billvsme '},{$set:{age:23}}) matches a message of name= ' Billvsme ' and then changes its age to 23
The $set is used here.
There are similar:

• $inc growth Db.stu.update ({name: ' billvsme '},{$Inc:{age:2}}) age increased by 2
• $Rename rename db.stu.update ({name: ' billvsme '},{$rename:{name: "Username"}}) Rename Name field to username
• $Setoninsert when Upsert, set the value of the field
• $unset Delete the specified column db.stu.update ({name: ' billvsme '},{$unset:{age:1}}) Delete the Age field

MongoDB Learning Note--curd operation