1 "Database Relationships" 数据库关系

Definition: A relationship exists between two database tables when one table has a foreign key that references the primary key of another table.

定义:当两个表中, 一个表的外键和另一个表的主键存在一种关联关系, 我们把这种关系称为数据库关系

2 "Many-to-Many Relationships" 多对多关系

Definition: Many-to-many relationships occur when each record in TableA may have many linked records in TableB and vice-versa.

定义: 如果存在这样一种关系: 表A中的一条记录和表B中有许多条记录关联. 反之亦然, 我们称这样的关系为多对多关系.

3 "One-to-Many Relationships"

Definition: One-to-many relationships occur when each record in TableA may have many linked records in TableB but each record in TableB may have only one corresponding record in TableA

定义: 如果存在这样一种关系: 表A中的一条记录和表B中有许多条记录关联. 相反的,在表B中,一条记录只对应表A中的一条记录, 我们称这种关系为一对多关系.

4 "One-to-One Relationships"

Definition: One-to-one relationships occur when there is exactly one record in the first table that corresponds to exactly one record in the related table.

定义: 在第一个表中,只有一条记录和它相关联的表的一条记录相对应,反之亦然.我们称这样的关系为:一对一关系.