1.Databases touch all aspects of our lives.

• Data will always have to be: stored, manipulated/accessed, shared, and transmitted. We can define database as a collection of related data that models some aspect of the real world. Also, databases are the core component of most computer applications.

2.Using file systems as data management has draw backs. Database systems offer solutions.

• Data redundancy and inconsistency. There might be dupliction of information in different files. And the files would have multiple formats.

• Difficulty in accessing data. There is always a new program needed to carry out a new task.

• Integrity problems. Intergrity constraints might be unnoticed, while in databases, they'll be clearly kept and stated. Also, it's hard to add/mordify constraints in file system. (need to be understanded by practise)

• Data isolation. Which is obvious.

• Atomicity of updates. Not quiet understand.

• Hard to allow concurrent access by multiple users. Uncontrolled concurrent accesses can lead to inconsistencies.

3.The field of databases deals with data, relationships, constraints, redundancy, data manipulation, transactions, concurrency, and scale. I'll find out exactly what they mean later.

4.About Data

• According to Elmasri/Navathe, data are known facts that can be recorded. There are two types of Data, one is unstructured, the other is structured.

5.About Database

• Database is a collection of related and structured data. Data items alone are relatively useless.

Database Management

• DBMS(Database Management System): Which manipulate and maintain databases.

• Database system: Database + DBMS.

Database Users

• DBAs(Database Administrator), Application Programmers, and End Users.

Design a Database

• Conceptual Design: Requirements can be represented and manipulated using some computerized tools so that it can be easily maintained, modified, and transformed into a database implementation.

• Logical Design: Translated by conceptual design that can be expressed in a data model implemented in a DBMS.

• Physical Design: Further specifications are provided for storing and accessing the database.

6.RDBMS(Relational DBMS)

Data Model

• Definition: concepts used to describe the allowed structure of a database.

• Levels of DM: High-level or conceptual (ER model for example), implementation or record-based, andd low-level or physical.

• Database Schema: a formalism of the data model, the structual description of what information will database hold.

• Database instance: any conbination of actual information populated in the database at a particular time.