Caused by: Java.sql.SQLException: Field ‘id’ doesn’t have a default value

如果主键的生成策略采取的是identity，而数据库中表的主键不是自动生成机制，则报这样的错误

org.hibernate.NonUniqueObjectException: a different object with the same identifier value was already associated with the session: [cn.itcast.hibernate717.helloworld.Person#1]

如果在hibernate中，有两个对象，但是其ID值是相同的，这样的情况在hibernate中是不允许出现 （在hibernate中，强调对象的唯一性）

Caused by: java.sql.BatchUpdateException: Cannot delete or update a parent row: a foreign key constraint fails (test/orders, CONSTRAINT FKC3DF62E58940CCE2 FOREIGN KEY (customer_id) REFERENCES customer (id))

违反了主外键约束的原则

org.hibernate.LazyInitializationException: could not initialize proxy - no Session

org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: cn.itcast.hibernate717.manytomany.Student