Definition, Functions, Components of a Database System (Database)
Definition of Database System
Database or database is a very important part in a data processing process. Database system is a collection of data that is stored neatly and systematically in a computer and can be processed or manipulated with software to produce useful or useful information. The data must be accessible in logically different sequences in a relatively easy way.
Database System Functions
1. Grouping Data
2. Avoiding Inconsistency or Duplicate Data
Database System Components
1.Hardware is hardware that supports database systems, such as Processor, Disk, Memory, and so on.
2. Operating system is the basis or support for various existing programs and systems, including database systems. Without an operating system, the database system will not be able to run. Examples of operating systems are Windows, Linux, and Mac OS.
3.DBMS (Database Management System) or Database Management System is software used to process or manage databases. Examples are MS Access, Oracle, SQL.
4. Database is all the data required and processed by the database system
5. User is the user of the database system. Here are some users who usually play a role in the database system.
DBA (Database Administrator), namely the user who is responsible for the entire database system, both in terms of control, and database backup.
Application Programmers, namely users who are in charge of developing programs to access the database.
Naive Users, namely end users who interact with programs created by application programmers without knowing how to create programs or existing programming languages.
Languages / Commands In SQL
DDL (Data Definition Language)
DDL is a command provided by SQL that can be used to build the framework of a database system, which includes databases, tables, stored procedures, or views. Usually, there are 3 commands used in this DDL, namely CREATE, ALTER, DROP.
CREATE
CREATE is the command used to create, its use is very easy, namely by including the type of structure and the name to be created. For example, if you want to create a database, you can use the CREATE DATABASE command database_name.
ALTER
ALTER is a command to change the structure that has been created. This command can be used to add, change, or delete columns in the table. How to use it is to include the type and name of the structure to be changed and the command to change.
Example: ALTER TABLE table_name ADD column_name data_type
DROP
The DROP command can be used to delete a database or table.
Example Usage: DROP DATABASE database_name
DML (Data Manipulation Language)
DML is a command provided by SQL to manipulate data in the database that has been created. In general, there are 4 commands that are often used, namely SELECT, INSERT, UPDATE, DELETE.
SELECT
The select function is used to retrieve data from a table in the database. How to use it is quite easy, you have to include the name of the table and the column taken.
Example: SELECT name_kolom1, nama_kolom2, nama_kolom3 FROM table_name
INSERT
INSERT is used to add new data to an existing table. The values entered into the table must match the number of columns in the table. For example, in table A there are 4 columns, so if you want to insert data, you must fill in all four columns.
Example: INSERT INTO table_name VALUES (long_name, nickname, short_name)
UPDATE
UPDATE command is used to change values or data in a table and is usually accompanied by certain conditions.
Example : UPDATE tableA SET value=100 WHERE name=”Amir”
DELETE
As the name implies, the delete command is used to delete data from the database. In practice in the field, the delete command is usually rarely used because data is usually only hidden or hidden from the user when the user chooses to delete certain data.
Example : DELETE FROM table_name WHERE name=”Amir”
DCL (Data Control Language)
DCL is a command provided by SQL to control access rights to data and databases. Commonly used commands are GRANT and REVOKE.
){kind=link}