spring data jpa
day1: an overview of orm thinking, hibernate, and jpa and basic operations of jpa
day2: springdata jpa’s operating principles and basic operations< br> day3: Multi-table operation, complex query

day1: Orm thought, hibernate and jpa overview and jpa basic operation

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First Orm Thought
　　 Main purpose: to manipulate entity classes It is equivalent to operating database tables
　　 establish two mapping relationships:
　　　　 mapping relationship between entity classes and tables
　　　　 mapping relationships between attributes in entity classes and fields in tables
　　 no longer focuses on: specific SQL statements

　　实现了ORM思想的框架：mybatis，hibernate 

第二hibernate框架介绍
Hibernate is an open source object-relational mapping framework,
It encapsulates JDBC,
It establishes a mapping relationship between POJOs and database tables, and is a fully automatic orm framework.

The third JPA specification
The full name of JPA is Java Persistence API, jpa is a set Based on the ORM specification, the internal is composed of interfaces and abstract classes.

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