Crow's Foot

Crow’s Foot merupakan alternatif diagram yang dapat digunakan untuk menggantikan simbol ER.

Gambar :

Relational Database

Relational Database?

A relational database stores data in separate tables instead of placing all data in one large table.
A relational database then allows Data Base Administrator’s (DBA’s) to define relationships between these tables.
These relationships enable DBA’s to combine data from several tables for querying and reporting.
This is accomplished through the use of keys, which are database fields used to uniquely identify specific records in a table.
Relational database technology allows databases to be larger, faster, and more efficient.
The concept of a relational database was first developed by Dr. Edger F. (Ted) Codd in A Relational Model of Data for Large Shared Data Banks in 1970. Dr. Codd defined thirteen standards which must be met before a database can be considered to be a relational database:

A relational DBMS must be able to manage databases entirely through its relational capabilities.

Types of Databases

Types of Databases

There are several common types of databases; each type of database has its own data model (how the data is structured). They include; Flat Model, Hierarchical Model, Relational Model and Network Model.

The Flat Model Database
In a flat model database, there is a two dimensional (flat structure) array of data. For instance, there is one column of information and within this column it is assumed that each data item will be related to the other. For instance, a flat model database includes only zip codes. Within the database, there will only be one column and each new row within that one column will be a new zip code.

Explanation of a Database Management System

In addition to the data itself, a set of program is necessary to facilitate adding new data as well as modifying and retrieving existing data within a database. This set of programs is referred to as database management system (DBMS).

Generally, the user of a database management system accesses the database via a special query language or via applications programs written in a high-level language. The applications program utilizes special host- or command-language instructions to communicate requests for data to the portion of the DBMS referred to as the database processing system. Basically, the database processing system consists of a series of programs that translate requests from users or user programs into the instructions necessary to access, add to, change, or delete records or items of data from database. Thus, an applications program need include only a command to access the desired data element. The actual mechanics of locating and accessing the data element are accomplished by the database processing programs.

Advantages and Disadvantages of Database

Advantages
– Reduced data redundancy
– Reduced updating errors and increased consistency
– Greater data integrity and independence from applications programs
– Improved data access to users through use of host and query languages
– Improved data security
– Reduced data entry, storage, and retrieval costs
– Facilitated development of new applications program