data type

  • The table below for MongoDB Several data types commonly used in :
  • Object ID: file ID
  • String: character string , The most commonly used , Must be effective UTF-8
  • Boolean: Store a Boolean value ,true or false
  • Integer: The whole number can be 32 Bit or 64 position , It depends on the server
  • Double: Store floating point values
  • Arrays: Array or list , Multiple values are stored in a key
  • Object: For embedded documents , That is, a value is a document
  • Null: Storage Null value
  • Timestamp: Time stamp
  • Date: Storing the current date or time UNIX Time format

object id

  • Every document has an attribute , by _id, Make sure every document is unique
  • You can set it yourself _id Inserted into the document
  • If not provided , that MongoDB Provides a unique... For each document _id, The type is objectID
  • objectID It's a 12 Hexadecimal number of bytes
    • front 4 Bytes are the current timestamp
    • Next 3 Byte machine ID
    • Next 2 In bytes MongoDB The service process of id
    • Last 3 A byte is a simple incremental value


  • grammar
db. Collection name .insert(document) 
  • When inserting a document , If you don't specify _id Parameters ,MongoDB The document is assigned a unique ObjectId
  • example 1
  • example 2

Simple query

  • grammar
db. Collection name .find()

to update

  • grammar
db. Collection name .update(
{multi: <boolean>}
  • Parameters query: Query criteria , similar sql sentence update in where part
  • Parameters update: Update Operators , similar sql sentence update in set part
  • Parameters multi: Optional , The default is false, Only the first record found is updated , The value is true It means to update all the documents that meet the conditions
  • example 3: Full document update
  • example 4: Specify property update , By the operator $set
  • example 5: Modify multiple matched data


  • grammar
db. Collection name .save(document) 
  • If the document _id Modify if it already exists , If the document _id Add if not

  • example 6{_id:'20160102','name':'yk',gender:1})
  • example 7{_id:'20160102','name':'wyk'})


  • grammar
db. Collection name .remove(
justOne: <boolean>
  • Parameters query: Optional , Conditions for deleted documents
  • Parameters justOne: Optional , If it is set to true or 1, Only one , Default false, Means to delete multiple
  • example 8: Delete only the first matching
  • example 9: Delete all

About size An example of

  • example 10
  • Create set
  • Insert the first database query
  • Insert the second database query
  • Insert the third database query
  • Insert the fourth database query
  • Insert the fifth database query

Data query

The basic query

  • Method find(): Inquire about
db. Collection name .find({ Condition document })
  • Method findOne(): Inquire about , Just return the first one
db. Collection name .findOne({ Condition document })
  • Method pretty(): Format the results
db. Collection name .find({ Condition document }).pretty()

Comparison operator

  • be equal to , Default is equal to judgment , There are no operators
  • Less than $lt
  • Less than or equal to $lte
  • Greater than $gt
  • Greater than or equal to $gte
  • It's not equal to $ne
  • example 1: The query name is equal to 'gj' Of the students
  • example 2: The query age is greater than or equal to 18 Of the students

Logical operators

  • When querying, there can be multiple conditions , Multiple conditions need to be connected by logical operators
  • Logic and : The default is the relationship between logic and
  • example 3: The query age is greater than or equal to 18, And the gender is 1 Of the students
  • Logic or : Use $or
  • example 4: Query age is greater than 18, Or gender is 0 Of the students
  • and and or Use it together
  • example 5: Query age is greater than 18 Or gender is 0 Of the students , And the name of the student is gj

Range operator

  • Use "$in","$nin" Judge whether it is in a certain range
  • example 6: Query age is 18、28 Of the students

regular expression

  • Use // or $regex Write regular expressions
  • example 7: Look up the student surnamed Huang
db.stu.find({name:/^ yellow /})
db.stu.find({name:{$regex:'^ yellow '}}})

Custom query

  • Use $where Then write a function , Return data that meets the criteria
  • example 7: Query age is greater than 30 Of the students
db.stu.find({$where:function(){return this.age>20}})

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