Oracle Learning Primer Series II Database Basics

The second of the Oracle Learning Primer series

Database Basics

This article toad to comb down those forgotten database basic knowledge, perhaps has not been remembered at all. In either case, remember to remember that you can write it down.

Here are a few questions to ask first:

What is the basic knowledge of the database?

Well, the toad just Spit and not die, read the catalogue to begin.

I e-mail:[email protected]

Public Number: Hoptoad

Welcome to communicate with all

1 Basic Concepts

Concept is the concept, everyone of these nouns do not die knock, but the definition must understand, understand the understanding of the party can grasp, the understanding of the creative after.

1.1 Data

data is a symbol that describes things, and is the basic object of database storage. Yes, that's right, the basic object, the database is used to store data, no data stored what? Of course the data comes from the thing itself, and any thing that contains a lot of information, the data needs to be abstracted from the things. For example, my mailbox, is [email protected], my address, Hangzhou Riverside, and so on, next door Lao Wang is also Hangzhou Riverside. Well, it's not normal, his address data must be the same as mine.

1.2 Database

A database (DATABASE,DB) is a collection of data that is organized, described, and stored by a certain data model. The data in the database has the small redundancy and the high data independence, can realize the data sharing, the database management system unifies the management.

Here are a few places to note:

The first is based on a certain data model of this very important, not just to get some data is still together;

2nd has a small redundancy and high and data independence, this is smaller and higher than some of our country some legal provisions of some, and so on, there is no specific indicators to consider, in this toad can only hehe ~

The third can achieve data sharing and unified management, this is very important, without this above features are more difficult to achieve.

1.3 Database management System

The system that manages the database is called the system software of the database Management system, DBMS.

such as Oracle,sybase,my SQL.

1.4 Database System

A database system is formed after the combination of database, database management system and computer system. Usually the database system consists of database, operating system, database management system, development tool, application system, database administrator and database user.

For example, an Oracle installation, create a database, and the server on the operating system, applications, etc. together become a database system.

2 Database Features

The basic concept of these, 4, remember even if the introduction, haha

Then let's look at the characteristics of the database, which are described in the database concept as well.

2.1 Data Structuring

It is the concept that, organized by a certain data model , is the face of all applications, not an application. Is the program itself a storage structure for an application?

2.2 Sharing

Database is for the entire system, for multiple users, multiple applications service, all need to share data, for different applications to store data to reduce redundancy, while providing data consistency.

2.3 Independence

Independence is primarily to consider the relationship with the application, decoupling the database from the application and allowing the database to run independently of the application.

2.4 Unified Management Control

Considering the difficulty of realizing the above 3 points, it is difficult to think, it is necessary to have a system, that is, database management system to unify the management of data security, integrity, concurrency, backup, recovery and so on.

3 Data Model

Database concept refers to the database is organized according to a certain data model, then 2 questions came

A) What is a data model?

b) Why do you want this data model?

The two questions are answered together.

So let's start with a little bit of it.

Data model: in software engineering , a data model is a model that defines how data is entered and output . There are three main elements: data structure, manipulation, data constraint.

A look at the three elements of the data model, Toad boring, data structure I remember is a major computer science curriculum, and toad itself learning machinery born, in this silently drifting.

In fact, the three main elements are the complement of the concept of digital model, the concept of data model expands is the concept of three major elements themselves. Of course this understanding may not be very good, we first remember the sentence: The data model is the abstraction of data characteristics.

The data model is divided into three types according to different application levels: Conceptual data Model, logical data model, physical data model.

The data model is divided into hierarchical model, net model, relational model and object-oriented model according to its structure.

The first question is basically over, let's go down.

The second question we look at the data model according to the classification of the application hierarchy, it is understood that the conceptual data model is a database user-oriented implementation of the world model, used to describe the world's conceptual structure, the model is independent of all database management systems, the logical model is the user to see, but also related to the database management system support, The model is user-oriented and system-oriented, and the physical model is a computer-oriented model, which describes the organizational structure of the data in the media, not only the database management system, but also the operating system, hardware and other related.

Here we understand that the data model describes how the data is stored in our computer step-by-step, the sum, this is not the concept of the database.

4 Database System Design steps

The database design is divided into 6 main stages:

1) Requirements Analysis phase

Collect the requirements of the system and establish the requirement documentation.

This is about knowing what the customer needs.

2) Conceptual Structure design phase

Synthesize, summarize and abstract the requirements, and form a conceptual model independent of the specific DBMS.

This is not a conceptual data model.

3) Logical Structure design phase

A logical database model supported by DBMS is derived based on the conceptual model, which satisfies the requirements of database access, consistency and operation.

This is the logical data model design.

4) Physical Structure design phase

Select a physical structure that best suits the application environment for the logical data model.

Well, this is the physical data model design.

5) Database Implementation phase

According to the design of the above structure to build a database, while the database system test run.

The code farmer starts coding to work.

6) database operation and Maintenance phase

The above 5 stages are the database development and design phase, in which the test part has been summed up inside.

At last the DBA brother appeared.

Oracle Learning Primer Series II Database Basics