![]() You may be familiar with the term object-relations impedance mismatch, which refers to the challenge of mapping data objects to a relational database. The relational model is flat, but developers can write queries to retrieve data and construct objects from that data. We can also use SQL (Structured Query Language) to retrieve and interact with data in individual tables and across multiple tables, using foreign key constraints. Programmers use foreign keys and join tables to define the relationships between entities-namely one-to-one, one-to-many, and many-to-many relationships. Entities are placed in tables where they occupy columns and rows. Java objects in a relational database context are defined as entities. ![]()
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