Use of mongodb

One 、 View all databases

 command ：show dbs

Use show dbs Command view database , There are currently three databases , Respectively ：admin、config、local

Two 、 Create database

 command ：use dataBaseName

Let's create user Database, for example

When we check the database, we find that it has not been created user This database .
If you want to create this database successfully , You must insert a data .
You can't insert data directly into the database , You can only go to the assembly collections Insert data .
Create a set and insert data with dot syntax .

 command ：db.collectionName.insert({
    })

We created student aggregate , And insert a piece of data . When viewing the database again , Find out user Database created successfully

3、 ... and 、 View all collections of the current database

 command ：show collections

Four 、 Table operations - newly added

 command ：db.collectionName.insert({
    })

We go on student Add new data to the set , Assemble in sql Is also called table

5、 ... and 、 Table operations - Inquire about

a. Check all records

db.student.find()

b. Query records with specified conditions , from find The first parameter of the method determines

Inquire about name For the record of Monkey King

db.student.find({
    name: ' The Monkey King '})

Inquire about name For Sunwukong and age by 20 The record of

db.student.find({
    name: ' The Monkey King ', age: 20})

Inquire about age Greater than 20 The record of

db.student.find({
    age: {
    $gt: 20}})

Inquire about age Less than 20 The record of

db.student.find({
    age: {
    $lt: 20}})

Inquire about age Greater than or equal to 20 The record of

db.student.find({
    age: {
    $gte: 20}})

Inquire about age Less than or equal to 20 The record of

db.student.find({
    age: {
    $lte: 20}})

Inquire about age Greater than or equal to 20 And less than or equal to 30 The record of

db.student.find({
    age: {
    $gte: 20. $lte: 30}})

Regular matching queries , It is generally used for specific condition query or fuzzy query , For example, inquire the record of surname sun

db.student.find({
    name: /^ Grandchildren /})

Or query , Inquire about age=20 or age=25 The record of

db.student.find({
    $or: [{
    age: 20}, {
    age: 25}]})

c. The query results only show the specified columns , from find The second parameter of the method determines , Only name Column sum age Column

db.student.find({
    }, {
    name: 1, age: 1})

d. The query results are arranged in ascending or descending order by the specified column （ 1 Ascending , -1 Descending ）

db.student.find().sort({
    age: 1})

e. Limit the number of queries , If the first five records are displayed

db.student.find().limit(5)

f. Query the records after the specified quantity , Such as query 2 Next record

db.student.find().skip(2)

The query in 5-10 Between the records , Can be used for pagination ,limit yes pageSize,skip What's the page *pageSize

db.student.find().limit(10).skip(5)

g. Look up the first record

db.student.findOne()
#  amount to 
db.student.find().limit(1)

h. Number of query records

db.student.find({
    age: {
    $gte: 25}}).count()
#  If you want to return the number of records after the limit , To use  count(true)
db.student.find({
    age: {
    $gte: 25}}).count(true)

6、 ... and 、 Table operations - modify

Modify use update Method , The first parameter is the query parameter , The second parameter is the modified content .
Such as ： Find the name Zhugeliang , Change the age to 100 year .

db.student.update({
    name: ' Zhugeliang '}, {
    $set:{
    age: 100}})
#  Modify the first record found by default , If you need to modify multiple records that meet the query parameters 
db.student.update({
    name: ' Zhugeliang '}, {
    $set:{
    age: 100}}, {
    multi: true})

If not $set, Replace complete . The second parameter will completely replace the record queried by the first parameter .

db.student.update({
    name: ' Zhugeliang '}, {
    age: 100})

Such as ： Find the name Zhugeliang , Add age to the original basis 100 year .

db.student.update({
    name: ' Zhugeliang '}, {
    $inc:{
    age: 100}})

7、 ... and 、 Table operations - Delete

#  Delete all queried records by default 
db.student.remove({
    name: ' Zhugeliang '}) 
#  If you only want to delete the first queried record 
db.student.remove({
    name: ' Zhugeliang '}, {
    justOne: true}) 

8、 ... and 、 Delete databases and collections

1. Delete database

use first use Switch to the specified database , Then use the following command to delete the current database

db.dropDatabase()

2. Delete the collection （ surface ）

# db.xxx Collection name .drop()
db.student.drop()