sajad torkamani

In a nutshell

In-memory objects (e.g., a Java / PHP object) and relational databases (e.g., MySQL) have different mechanisms for structuring and representing data. Often, object representations such as collections or inheritance don’t map neatly to relational databases.

The Data Mapper is the layer of software that transfers data between the two structures whilst keeping them isolated. The in-memory objects don’t need to know about the database and vice-versa.

Other notes