MongoDB basic operations

Basic operation

• MongoDB stores data as a document, and the data structure consists of key-value (key=>value) pairs
• MongoDB documents are similar to JSON objects, and field values ​​can contain other documents, arrays, arrays of documents
• Install and manage the mongodb environment
• Complete database and collection management
• Data addition, modification, deletion, query

noun

SQL terms/concepts	MongoDB terms/concepts	explain
database	database	database
table	collection	Database table/collection
row	document	Data record line/document
column	field	data field/domain
index	index	index
table joins		Table joins, MongoDB does not support
primary key	primary key	Primary key, MongoDB automatically sets the _id field as the primary key

• Three elements: database, collection, document
  • A collection is a table in a relational database
  • Documents correspond to rows in a relational database
• A document is an object composed of key-value pairs, which is an extended Bson form of json

{'name':'guojing','gender':'男'}

• Collection: Similar to a table in a relational database, it stores multiple documents, and the structure is not fixed. For example, the following documents can be stored in a collection

{'name':'guojing','gender':'男'}
{'name':'huangrong','age':18}
{'book':'shuihuzhuan','heros':'108'}

• Database: is a physical container for a collection, a database can contain multiple documents
• A server usually has multiple databases

Install

• Download the version of mongodb, two points
  • According to industry rules, the even number is the stable version, such as 1.6.X, and the odd number is the development version, such as 1.7.X
  • 32bit mongodb can only store up to 2G of data, 64bit has no limit
• Go to the official website and select the appropriate version to download
• decompress

tar -zxvf mongodb-linux-x86_64-ubuntu1604-3.4.0.tgz

• Move to the /usr/local/ directory

sudo mv -r mongodb-linux-x86_64-ubuntu1604-3.4.0/ /usr/local/mongodb

• Add the executable to the PATH path

export PATH=/usr/local/mongodb/bin:$PATH

manage mongo

• The configuration file is in /etc/mongod.conf

• Default port 27017

• start up

sudo service mongod start

• stop

sudo service mongod stop

• connect using terminal
• This shell is the client of mongodb and a js compiler.

mongo

• Order

db查看当前数据库名称
db.stats()查看当前数据库信息

• Terminal exits connection

exit
或ctrl+c

• GUI: robomongo, find the running program in the bin directory after decompression
• The interface is as follows:

database switch

• View the current database name

db

• View all database names
• List all databases that exist physically

show dbs

• switch database
• If the database does not exist, point to the database, but not create it, the database is not created until data is inserted or the collection is created

use 数据库名称

• The default database is test, if you do not create a new database, the collection will be stored in the test database

database delete

• delete the currently pointed database
• Do nothing if the database does not exist

db.dropDatabase()

Collection creation

• grammar

db.createCollection(name, options)

• name is the name of the collection to create
• options is a document that specifies the configuration of the collection
• The options parameter is optional, so only need to specify the collection name. The following is a list of options that can be used:
• Example 1: Unlimited collection size

db.createCollection("stu")

• Example 2: Limit the size of the set, and you can view the effect after learning to insert a statement
• Parameter capped: The default value is false, which means no upper limit is set, and the value is true, which means setting the upper limit.
• Parameter size: When the capped value is true, this parameter needs to be specified, indicating the upper limit size. When the document reaches the upper limit, the previous data will be overwritten, in bytes

db.createCollection("sub", { capped : true, size : 10 } )

View a collection of the current database

• grammar

show collections

delete

• grammar

db.集合名称.drop()

type of data

• The following table shows several data types commonly used in MongoDB:
• Object ID: Document ID
• String: String, most commonly used, must be valid UTF-8
• Boolean: stores a boolean value, true or false
• Integer: Integer can be 32-bit or 64-bit, depending on the server
• Double: store floating point value
• Arrays: Arrays or lists, where multiple values ​​are stored into one key
• Object: for embedded documents, i.e. one value for one document
• Null: store Null value
• Timestamp: Timestamp
• Date: UNIX time format to store the current date or time

object id

• Each document has an attribute, _id, which guarantees the uniqueness of each document
• You can set the _id to insert the document yourself
• If not provided, then MongoDB provides each document with a unique _id of type objectID
• objectID is a 12-byte hexadecimal number
  • The first 4 bytes are the current timestamp
  • Next 3 bytes of machine ID
  • MongoDB's service process id in the next 2 bytes

The last 3 bytes are simple increment values

insert

• grammar

db.集合名称.insert(document)

• When inserting a document, if you do not specify the _id parameter, MongoDB will assign a unique ObjectId to the document
• Example 1

db.stu.insert({name:'gj',gender:1})

• Example 2

s1={_id:'20160101',name:'hr'}
s1.gender=0
db.stu.insert(s1)

Simple query

• grammar

db.集合名称.find()

renew

• grammar

db.集合名称.update(
   <query>,
   <update>,
   {multi: <boolean>}
)

• Parameter query: query condition, similar to the where part in the sql statement update
• Parameter update: update operator, similar to the set part of the sql statement update
• Parameter multi: optional, the default is false, which means that only the first record found is updated, and a value of true means that all documents that meet the conditions are updated
• Example 3: Full document update

db.stu.update({name:'hr'},{name:'mnc'})

• Example 4: Specify attribute update, through operator $set

db.stu.insert({name:'hr',gender:0})
db.stu.update({name:'hr'},{$set:{name:'hys'}})

• Example 5: Modify multiple matched data

db.stu.update({},{$set:{gender:0}},{multi:true})

keep

• grammar

db.集合名称.save(document)

• Modify if the document's _id already exists, add if the document's _id does not exist

• Example 6

db.stu.save({_id:'20160102','name':'yk',gender:1})

• Example 7

db.stu.save({_id:'20160102','name':'wyk'})

delete

• grammar

db.集合名称.remove(
   <query>,
   {
     justOne: <boolean>
   }
)

• Parameter query: optional, the condition of the deleted document
• Parameter justOne: optional, if set to true or 1, only one item will be deleted, the default is false, which means that multiple items will be deleted
• Example 8: delete only the first match

db.stu.remove({gender:0},{justOne:true})

• Example 9: Delete all

db.stu.remove({})

example about size

• Example 10
• Create a collection

db.createCollection('sub',{capped:true,size:10})

• Insert the first database query

db.sub.insert({title:'linux',count:10})
db.sub.find()

• Insert second database query

db.sub.insert({title:'web',count:15})
db.sub.find()

• Insert the third database query

db.sub.insert({title:'sql',count:8})
db.sub.find()

• Insert the fourth database query

db.sub.insert({title:'django',count:12})
db.sub.find()

• Insert the fifth database query

db.sub.insert({title:'python',count:14})
db.sub.find()

data query

Basic query

• Method find(): query

db.集合名称.find({条件文档})

• Method findOne(): query, only return the first one

db.集合名称.findOne({条件文档})

• Method pretty(): format the result

db.集合名称.find({条件文档}).pretty()

comparison operator

• Equal, default is equal to judgment, no operator
• less than $lt
• less than or equal to $lte
• greater than $gt
• greater than or equal to $gte
• not equal to $ne
• Example 1: Query for students whose name is equal to 'gj'

db.stu.find({name:'gj'})

• Example 2: Query students whose age is greater than or equal to 18

db.stu.find({age:{$gte:18}})

Logical Operators

• There can be multiple conditions when querying, and multiple conditions need to be connected by logical operators
• Logical AND: The default is a logical AND relationship
• Example 3: Query students whose age is greater than or equal to 18 and whose gender is 1

db.stu.find({age:{$gte:18},gender:1})

• Logical OR: use $or
• Example 4: Query students whose age is greater than 18, or whose gender is 0

db.stu.find({$or:[{age:{$gt:18}},{gender:1}]})

• and is used with or
• Example 5: Query students whose age is greater than 18 or whose gender is 0, and the student's name is gj

db.stu.find({$or:[{age:{$gte:18}},{gender:1}],name:'gj'})

range operator

• Use "$in", "$nin" to determine whether it is within a certain range
• Example 6: Query students whose ages are 18 and 28

db.stu.find({age:{$in:[18,28]}})

Support regular expressions

• Write regular expressions using // or $regex
• Example 7: Query students with the surname Huang

db.stu.find({name:/^黄/})
db.stu.find({name:{$regex:'^黄'}}})

custom query

• Write a function after $where to return the data that meets the conditions
• Example 7: Query students whose age is greater than 30

db.stu.find({$where:function(){return this.age>20}})

Limit

• Method limit(): used to read a specified number of documents
• grammar:

db.集合名称.find().limit(NUMBER)

• The parameter NUMBER indicates the number of documents to be obtained
• If no arguments are specified, display all documents in the collection
• Example 1: Query 2 pieces of student information

db.stu.find().limit(2)

skip

• Method skip(): used to skip a specified number of documents
• grammar:

db.集合名称.find().skip(NUMBER)

• The parameter NUMBER indicates the number of skipped records, the default value is 0
• Example 2: Query student information starting from item 3

db.stu.find().skip(2)

use together

• The methods limit() and skip() can be used together, in no particular order

• Create a dataset

for(i=0;i<15;i++){db.t1.insert({_id:i})}

• Querying data from 5 to 8

db.stu.find().limit(4).skip(5)
或
db.stu.find().skip(5).limit(4)

projection

• In the returned results of the query, only the necessary fields are selected, rather than the entire field of a document
• For example: a document has 5 fields, only 3 need to be displayed, and 3 of them can be projected
• grammar:
• The parameter is a field and a value, a value of 1 means display, and a value of 0 does not display

db.集合名称.find({},{字段名称:1,...})

• For the fields that need to be displayed, set it to 1, otherwise it will not be displayed
• Special: For the _id column, it is displayed by default. If it is not displayed, it needs to be explicitly set to 0
• Example 1

db.stu.find({},{name:1,gender:1})

• Example 2

db.stu.find({},{_id:0,name:1,gender:1})

sort

• The method sort() is used to sort the result set
• grammar

db.集合名称.find().sort({字段:1,...})

• Parameter 1 is in ascending order
• Parameter -1 is for descending order
• Example 1: Descending by gender, then ascending by age

db.stu.find().sort({gender:-1,age:1})

Statistics

• The method count() is used to count the number of documents in the result set
• grammar

db.集合名称.find({条件}).count()

• can also be used with

db.集合名称.count({条件})

• Example 1: Counting the number of boys

db.stu.find({gender:1}).count()

• Example 2: Count the number of boys over the age of 20

db.stu.count({age:{$gt:20},gender:1})

Eliminate duplicates

• The method distinct() deduplicates the data
• grammar

db.集合名称.distinct('去重字段',{条件})

• Example 1: Find genders whose age is greater than 18 (de-duplication)

db.stu.distinct('gender',{age:{$gt:18}})