What is the difference between an ORM and an ODM?

问题:

I am trying to figure out what the difference is between ORM and ODM, as far as I understand the concept, ORM (Object Relational Mapper) maps the relations between data, where as ODM (Object Document Mapper) deals with documents. Am I right in assuming that mySQL is an example of ORM and MongoDB is a example of ODM?

As I am sure you can see, I am not too familiar with the theory of the concept. Could someone please clarify the differences between the two?

回答1:

MySQL is an example of a relational database - you would use an ORM to translate between your objects in code and the relational representation of the data.

Examples of ORMs are nHibernate, Entity Framework, Dapper and more...

MongoDB is an example of a document database - you would use an ODM to translate between your objects in code and the document representation of the data (if needed).

Mandango is an example of an ODM for MongoDB.

回答2:

An ORM maps between an Object Model and a Relational Database. An ODM maps between an Object Model and a Document Database. MySQL is not an ORM, it's a Relational Database, more specifically, a SQL Database. MongoDB is not an ODM, it's a Document Database.

回答3:

Essencially, an ORM use a SQL database Driver like ODBC, JDBC or OLEDB to translate the object notation to relational notation and an ODM use a JSON or JSONB api to translate the Object notation to Document notation.

There are different kind of implementations under the hood.

PS: JSONB is a JSON text document notation stored in a binary format as used by MongoDB.

回答4:

Mongoose is a good example for ODM(Object Data Model) for MongoDB in which you can directly perform operations with objects and that gets translated into the appropriate query and schema. It can be found Here at https://mongoosejs.com/