光阴冢 赛博空间的自留地

DBS - Relational Model

QAQ.

For such a long time I didn’t read this book.

Relational Model

In my opinion, the relational model is a mathematical model to describe the theory behind the RDBMS( Relational Database System), so it can represent some items or objects more clearly than sentences.

Relation

Relation is just a table. And it has some rows and colomns.

Attribute

In a relation, there are some colomns, and a named colomns is called an attribute.

Domain

Each attribute must have some constraints to its value. So, the domain is the set of allowable values for one or more attributes.

Tuple

It is a row of a relation.(or in a table)

Relational database

A collection of normalized relations with distinct relation names. Normalized is explained as “appropriately structured”. Some….Kind of ? Maybe I can understand but can’t tell.

Other Terms

Degree, cardinality.