Mongodb common commands

Select and create databases

use Database name

If the database exists, select it , If the database does not exist, it will be created automatically . The following statement creates
commentdb database ：
use commentdb

view the database ：show dbs
But you won't see the database you created , In essence, it has not been created , Only after you actually perform the write operation can you create .

View set , You need to select the database first , To view the collection of this database ：show collections

After the database is created , You don't have to create collections , Insert data directly ,

Insert and query documents

After selecting the database , Use collections to manipulate documents , Insert document syntax format ：
db. Collection name .insert( data );

Insert the following test data ：
db.comment.insert({content:“ The tenth power course ”,userid:“1011”})

The syntax format of the query set ：
db. Collection name .find()

Inquire about spit All documents in the collection , Enter the following command ：
db.comment.find()

There will be a file called _id Field of , This is equivalent to the primary key of the table in our original relational database , This field is not specified when you insert a document record ,MongoDB Automatically created , The type is ObjectID type . If we specify this field when inserting a document record, we can also , Its type can be ObjectID type , It can also be MongoDB Any type supported .
Test statement

db.comment.insert({
    _id:"1",content:" Why did it go wrong ",userid:"1012",thumbup:2020});
db.comment.insert({
    _id:"2",content:" Work overtime until midnight ",userid:"1013",thumbup:1023});
db.comment.insert({
    _id:"3",content:" What if the mobile traffic exceeds ",userid:"1013",thumbup:111});
db.comment.insert({
    _id:"4",content:" perseverance prevails ",userid:"1014",thumbup:1223});

In the same set , Data composition can be different .

Query according to certain conditions , Such as query userid by 1013 The record of , As long as find() Add parameters to , So are the parameters json Format , as follows ：
db.comment.find({userid:‘1013’})

Just return the first data that meets the conditions , We can use findOne Command to implement ：
db.comment.findOne({userid:‘1013’})

Return the specified number of records , Can be in find After the method is called limit To return results , for example ：
db.comment.find().limit(2)

Modifying and deleting documents

Modify the syntax structure of the document ：
db. Collection name .update( Conditions , Revised data )

modify _id by 1 The record of , Thumb up for 1000, Enter the following statement ：
db.comment.update({_id:“123”},{thumbup:1000})

It was found after execution that , This document is in addition to thumbup The other fields are missing .

To solve this problem , We need to use modifiers $set To achieve , The order is as follows ：
db.comment.update({_id:“123”},{$set:{“name”:“ Zhang San ”}})
This field can be modified if any , Add this field without

Delete the syntax structure of the document ：
db. Collection name .remove( Conditions )

The following statement can delete all the data , Use with caution ~ Delete all data
db. Collection name .remove({})

Delete conditions can be placed in braces , Delete... For example thumbup by 1000 The data of , Enter the following statement ：
db. Collection name .remove({thumbup:1000})

Count the number

Use of statistical record conditions count() Method . Statistics of the following statements spit The number of records in the collection ：
db. Collection name .count()

Statistics by condition , For example, statistics userid by 1013 The number of records ：
db.comment.count({userid:“1013”})

Fuzzy query

MongoDB The fuzzy query is realized by regular expression . The format is ：
/ Fuzzy query string /

Query comments contain “ Traffic ” All documents of , The code is as follows ：
db.comment.find({content:/ Traffic /})

Query comments with “ Work overtime ” At the beginning ,
db.comment.find({content:/^ Work overtime /})
Query comments with “ Work overtime ” At the end of the ,
db.comment.find({content:/ Work overtime $/})

Greater than Less than It's not equal to

db. Collection name .find({ “field” : { $gt: value }}) // Greater than : field > value
db. Collection name .find({ “field” : { $lt: value }}) // Less than : field < value
db. Collection name .find({ “field” : { $gte: value }}) // Greater than or equal to : field >= value
db. Collection name .find({ “field” : { $lte: value }}) // Less than or equal to : field <= value
db. Collection name .find({ “field” : { $ne: value }}) // It's not equal to : field != value

The number of query comment likes is greater than 1000 The record of ：db.comment.find({thumbup:{$gt:1000}})

Inclusion and exclusion

Include use $in The operator
Query the comments collection userid Field contains 1013 and 1014 Documents ：
db.comment.find({userid:{$in:[“1013”,“1014”]}})

Does not include the use of KaTeX parse error: Expected '}', got 'EOF' at end of input: ….find({userid:{ nin:[“1013”,“1014”]}})

Conditional connection

If we need to satisfy the above two conditions at the same time , Need to use $and Operator to associate conditions （ amount to SQL Of and）. The format is ：
KaTeX parse error: Expected '}', got 'EOF' at end of input: ….comment.find({ and:[ {thumbup:{ KaTeX parse error: Expected 'EOF', got '}' at position 9: gte:1000}̲} ,{thumbup:{ lt:2000} }]})

If the relationship between two or more conditions is or , We use operators for association , With the front and It's the same way , The format is ：
KaTeX parse error: Expected '}', got 'EOF' at end of input: ….comment.find({ or:[ {userid:“1013”} ,{thumbup:{$lt:2000} }]})

Column value growth

Increase or decrease the value of a column on the basis of the original value , have access to $inc Operator ： To give a negative number is to reduce
db.comment.update({_id:“2”},{$inc:{thumbup:1}})