MongoDB Switch Database Command

Switching Database

• In the shell, db refers to the current database.
• To display the current database, type db.
• The default database is test.
• To switch databases, use the use command, for example, use seedinfotech.

Creating a Collection

• To create a collection in the database, use db.createCollection("CollectionName").
• For example, db.createCollection("Employee").
• If a collection does not exist, MongoDB creates it when you first store data for that collection.

Inserting Data

• To insert data into a collection, use db.CollectionName.insertOne({document}).
• For example, db.Student.insertOne({'eid':101, 'name': "Jagruti"}).
• To check collections, use show collections.
• To show collection of documents, use db.CollectionName.find().

Dropping a Collection or Database

• To drop a collection, use db.CollectionName.drop().
• For example, db.Student.drop().
• To drop a database, use db.dropDatabase().

MongoDB Documents

• MongoDB stores data records as BSON (Binary Javascript Object Notation) documents.
• BSON is a binary representation of JSON documents, though it contains more data types than JSON.
• Documents are composed of field-and-value pairs.
• The value of a field can be any of the BSON data types, including other documents, arrays, and arrays of documents.

Document Structure

• Documents have the following structure: { field1: value1, field2: value2, field3: value3,...fieldN: valueN }.
• Field names are strings.
• Field names have restrictions, such as:
  • The field name _id is reserved for use as a primary key; its value must be unique in the collection, is immutable, and may be of any type other than an array.
  • If the _id contains subfields, the subfield names cannot begin with a ($) symbol.
  • Field names cannot contain the null character.
  • The server permits storage of field names that contain dots (.) and dollar signs ($).