- 一张表对应一个关系 (relation)，行对应元组 (tuple)，列对应属性 (attribute)
- 码 key
- is a superkey of is values for are sufficient to identify a unique tuple of each possible relation
- is a condidate key is is minial superkey
- is a primary key, if K is a candidate key and is defined by user explicitly
- Foreign key Assume there exists relations and : , , we can say that attribute in relation is foreign key referencing , and is a referencing relation, and is a referenced relation.
关系代数是 Relational Model 的数学基础，详见 Relational algebra
SQL：结构化查询语言，分为 DDL,DML,DCL 几种类型，详见 SQL