Oracle 11g Overview Chaper1

1. Relational model
2. E-r model
3. Paradigm

1. Brief description of Oracle

Oracle is a powerful database software developed by 1977 IBM.

2. Basic theory of relational data

• relational database and database management system

1) database is due to the information resources (a large number of data) management needs, the explosion of information resources, database management technology has also been improved (manual management, file system, database system), the data model has: Hierarchical model, network model, relational model, object-oriented model.

2) The relational database is based on the relational model, and the relationship model represents the connection between the real world entities.

In a relational data model, a relationship can be seen as a normalized two-dimensional table of rows and columns (so the relational data structure is simple, clear, and data independence is high) h

Two-dimensional tables: Each row in a table is called a tuple, which is an entity in the Entity Collection (table), and each tuple in the table satisfies the same relationship

Each column in the table is called a property, the property name in the table cannot be the same, and the column's value range becomes the domain

A table is a collection of a relationship

The normalization of two-dimensional tables: attributes are atomic, i.e. they cannot be divided

There are no duplicate tuples, that is, there are no duplicate rows

A primary key uniquely identifies a tuple that satisfies any two rows in the table that are not the same constraint

Foreign KEY (a non-primary key attribute in the primary table is the primary key of the referenced table)

• E-R Model of relational database

Composition of the E-R Model: 1) Entity: an objective and indivisible thing in the real world, such as a student

2) Attributes: Each entity is represented by a property, such as student (school number, age, gender, Class)

3) Contact: Relationship between entities (one-to-one, one-to-many, many-to-many)

• Design paradigm of relational database

Normalization is the process of organizing a database into a structure that minimizes redundant data while preserving the integrity of stored data (paradigms have first to sixth paradigms and bcnf paradigms)

First paradigm: Relationships (tables) any two tuples are not the same and each attribute value is a single indivisible

Second paradigm: There are primary keys in the database that can uniquely distinguish each entity

The third paradigm: no non-critical fields in the relational table are transitive dependent on any candidate fields (A->b, B->c, a->c) are not present

Oracle 11g Overview Chaper1