Master MongoDB: Essential Commands for Creating, Querying, and Managing Databases

Creating and Switching Databases

Use the use DATABASE_NAME command to switch to an existing database or create a new one if it does not exist.

use mikechen

Viewing Databases

List all databases on the server with:

show dbs

Deleting a Database

Switch to the target database and then drop it:

use DATABASE_NAME
db.dropDatabase()

Inserting Documents

Insert a document into a collection using insert:

db.users.insert({
  name: "小张",
  age: 19,
  gender: 1,
  address: "广州",
  isDelete: 0
})

Updating Documents

Update matching documents with update and the $set operator (similar to SQL UPDATE):

db.users.update({username: "smith"}, {$set: {country: "Canada"}})

Querying Documents

Retrieve all records: db.users.find() Count the total number of records: db.users.find().count() Get distinct values for a field: db.users.distinct("name") Conditional query (e.g., age equals 28): db.users.find({"age": 28}) Pagination (limit and skip):

db.users.find().limit(5).skip(2)

Fuzzy Search

Find documents where the name field matches a regular expression:

db.users.find({name: /mikechen/})

Deleting Documents

Remove all documents from a collection: db.products.remove({}) Remove documents matching a condition (e.g., age greater than 20): db.users.remove({age: {$gt: 20}}) Delete all documents in a collection using deleteMany:

db.collection.deleteMany({})