【DB】database introduction

database applications:

– Banking System,
– Stock Market,
– Transportation,
– Social Network,
– Marine Data Analysis,
– Criminal Analysis and Control,
– Now, BIG DATA....

• Develop a good database system:
– Effectively organize data (database design).
– Efficiently execute users queries (transaction management)

- nowadays we need:

　　huge dataset & effectively & efficiently

 

what is database?

1. a collection of related data

2. the data have some structure

3. data items alone are relatively useless

4. can be manipulated by a database management system.(DBMS)

 

waht is a  DBMS?

a collection of programs that enables users to create and maintain a database.

 

what is a database system?

database system = database + DBMS

what does a database system do?

1. define a database  2. construct a database 3. manipulate a database(querying and updating)  4. reporting

so.. it must be..

timely(及時) ; multi-user; modifiable; secure; no redundancy; robust(健壯)

 

why we need meta-data?

To allow a general DBMS to be applied to a particular database application, we need meta-data

traditional file storage method(file processing) is very redundancy.

meta-data is a database method, it only defined once.

what is meta-data?

a defination and description of the stored database, such as stucture of each file, type and storage format of each data item, constraints etc.

it stored in the system catalog.

what is the pros/benifits of using mata-data?

1.  program-data independence -- DBMS access programs may be written independent of file structures and storage formats.

2. data abstraction -- info hiding

3. support for views. -- different users can have different views of the database

 

Database personnel

1. database administrator(DBA)   --- centralised control

　　authorising access; monitoring usage; recovery; identifying the data; choosing appropriate stuctures; managing definitions of view.

2.End user -- people do querying, updating , reporting, etc.

　　(1) Naive user : use DB by a menu system

　　(2) Online user: design their own queries  

3. System analyst

　　determine end users requirements;

　　devolop specifications for canned transactions and reports;

　　database design.

4.Application programmer --- implements the specifications given by analyst

　　test; debug; maintains the resulting programs.

 

Database concepts

data model: a set of concepts that is used to describe the allowed structure of a database.(e.g. ER-model)

data schema: an instance of a data model.

 

ANSI-SPARC three level architecture with database language

View definition language(VDL):　　　　external/view level (extenral schemas or user views)

Data definition language(DDL):　　　　conceptual level(conceptual schema, tells the stucture of database )

Storage definition language(SDL): 　　internal level (internal schema, physical storage structure)