ความรู้เบื้องต้นฐานข้อมูล 1

A database is a structured collection of records or data.

Database management systems (DBMS) are the software used to organize and maintain the database. Example is MS Access, SQL Server

Early 1970 the Database was used term in Europe and USA.

1960s, the first developed DBM by Charles Bachman.

1970, the relational model was proposed by E. F. Codd.

1990s, attention shifted to object-oriented databases.

2000s, the fashionable area for innovation is the XML database

Bit Byte Field Record File Entity Attribute Primary Key Foreign Key Field Type

A bit is a binary digit, taking a value of either 0 or 1.

A byte is a unit of measurement of information storage, most often consisting of eight bits.

1024 bytes= 1KB 1024 KB = 1MB 1024 MB = 1GB 1024 GB = 1 Terabyte (TB) Petabyte Exabyte Zettabyte Yottabyte Brontobyte

One or more related characters treated as a unit and constituting part of a record.

A group of related data, words, or fields treated as a meaningful unit.

A group of records in database.

an entity is an existing or real thing. Example: Customer, Student, Item

an attribute is an specification that defines a property of an object, element, or file.

Example:CustomerAttribute: Title, Firstname, Lastname,

Address, Telephone, Email

Primary key is that candidate key which is used to uniquely identify each and every attribute and instance of a particular entity.

Example – Purchase Order Master Table

A Foreign key is an attribute in some another entity which is already a primary key in some entity. Is used for the purpose of maintaining the integrity of the data.

Example – The Purchase Order Master and the Purchase Order Detail Relationship.

Text. Essentially the strings or number. 255 character maximum.

Number. This category includes Byte (unsigned 8-bit), Integer (signed 16-bit), Long (signed 32-bit), Single (signed 32-bit), and Double (signed 64-bit).

Currency. A 64-bit fixed point number, designed to give the accuracy needed for financial data. 15 digits of whole dollars, plus four decimal places (hundredths of a cent).

The AutoNumber is an automatically assigned number.

Date/Time. The 8-byte floating point numbers, the integer part refers to the day, and the fraction part refers to the time.

Yes/No. A Logical field can be displayed as Yes/No, True/False, or On/Off.

Memo. Many texts. Up to 64K of text.

OLE Object. Use this type to store pictures, audio, video, or other BLOBs (Binary Large OBjects).

User Operator System Analyst Programmer Database Administrator

It defines a set of operations that can be performed on the data.

Hierarchical database model Network database model Relational database model Object database models

Alternative › Star schema› XML database

hierarchical database model, data is organized into a tree-like structure. The structure allows repeating information using parent/child relationships: each parent can have many children but each child only has one parent.

network model is a database model conceived as a flexible way of representing objects and their relationships. the network model allows each record to have multiple parent and child records

A relational database model developed by E.F. Codd. A relational database allows the definition of data structures, storage and retrieval operations and integrity constraints. In such a database the data and relations between them are organised in tables. A table is a collection of records and each record in a table contains the same fields.

A data model is a logic organization of the real world objects (entities), constraints on them, and the relationships among objects. A DB language is a concrete syntax for a data model. A DB system implements a data model.

The star schema is the simplest style of data warehouse schema. The star schema consists of a few "fact tables" (possibly only one, justifying the name) referencing any number of "dimension tables".

An XML database is a data persistence software system that allows data to be stored in XML format.

XML Format› <firstname> Witoon </firstname>› <lastname>Thammatuch-aree</

lastname>

One to Many Many to One One to One Many to Many

One to Many relationship – occurs when one entity is related to many occurrences in another entity. For example, one club has many members.

A Many to One relation is the same as one-to-many, but from a different viewpoint.

A one-to-one relation is exception in databases. It can occur, but it's often a sign that the database design has opportunities for improvement.

Many to Many relationship – occurs when one entity is related to many occurrences in one entity. For example, one newspaper has many readers and one reader has many newspaper.

Avoid Inconsistency Data Sharing Reduce Redundancy Data Integrity Data Security Application and Database

Create Table and Relation for:› Group A = Customers› Group B = Suppliers› Group C = Employees› Group D = Items

Field name, Field type, Field size, Primary Key