is a set of data written in a strictly defined manner in corresponding structures

assumed data model. In the present case data and computer are included

A program that specializes in the collection and processing of these data. The database

is composed of different elements. The most important of them is a record split into several

The fields in which the information for each category is stored. For example, in

Address Book Each record is a collection of information about one person. It consists of

Several fields that hold such information as name, address, telephone number, etc.

Each field contains data for a separate category.


Relational Database Management System (RDBMS, literally a management system

relational database) is a set of programs used to use a database

based on the relational model.


Structural query language used to create, modify databases and to

Placing and retrieving data from databases. SQL is a declarative language.

The decision to store and download data is left to the system

Database management (DBMS). The use of SQL, according to its name, consists in

querying the database. Queries can be counted as one of three

major subsets:

• SQL DML (Data Manipulation Language)

• SQL DDL (“Data Definition Language”),

• SQL DCL (Data Control Language).


DML (Data Manipulation Language) is used to perform data operations – to them

inserting, deleting, viewing, changing. The most important command of this

The set is:

• SELECT – retrieve data from the database,

• INSERT – data entry in the database,

• UPDATE – change data,

• DELETE – delete data from the database.


With DDL (Data Definition Language) you can operate on data structures

are stored – ie, add, change and delete tables or databases.

The most important commands of this group are:

• CREATE (eg CREATE TABLE, CREATE DATABASE, …) – create a structure

(database, table, index, etc.)

• DROP (eg DROP TABLE, DROP DATABASE, …) – removal of structure,

• ALTER (eg ALTER TABLE ADD COLUMN …) – change the structure (add a column

to the table, change the data type in the table column).


The DCL (Data Control Language) is used to grant object permissions

database. The most important commands in this group are:


OPTION) – grant all rights to the EMPLOYEES table to the PIOTR user

An option allows you to assign rights to this table.

• REVOKE – the user has been given all rights to the table that were given

granted by the GRANT command.