MongoDB Learning notes-common commands

Here's a record of what MongoDB often commands

Database related

Create a database

Use database_name

If the database does not exist, create the database, or switch to the specified database.

Delete database : Switch to the database you want to delete, execute the command.

Db.dropdatabase ()

View all databases

Show DBS

Collection related

View all Collections

Show tables

Delete the specified collection : Replace the collection_name of the following command with the execution

Db. collection_name. Drop ()

Document related

Insert Document

Db. Collection_name.insert (document)

Insert document You can also use the Db.col.save command. If you do not specify the _id field, the Save () method is similar to the Insert () method. If the _id field is specified, the data for the _id is updated.

Update document

db.collection.update (   <query>,   <update>,   {     <  Boolean>,     <boolean>,     <document>   }) 

Parameter description:

• Query: The search condition for update, similar to where in SQL update query.
• Update: Update object and some updated operators (such as $, $inc ... ) can also be understood as the SQL update query within the set after the
• upsert : Optional, this parameter means that if there is no record of update, insert objnew,true as INSERT, default is False, do not insert.
• multi : Optional, mongodb default is False, only update the first record found, if this parameter is true, will be found on the condition of a number of records update all.
• writeconcern : Optional, throws an exception level.

Delete a document

db.collection.remove (   <query>,   {     <boolean>,     <document>   })

Parameter description:

• query : (optional) The condition of the deleted document.
• justone : (optional) If set to TRUE or 1, only one document is deleted.
• Writeconcern : (optional) the level at which the exception is thrown.

Querying documents

Db.collection.find (query, projection)

Parameter description:

• query: Optional, use the query operator to specify the criteria
• projection : Optional, use the projection operator to specify the returned key. Returns all the key values in the document when queried, just omit the argument (omitted by default).

MongoDB Learning notes-common commands