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Introduction to SQL

What is SQL?

SQL (Structered Query Language), SQL is definitely not a programming language. As a sub-language, it is used for database operations, and the general syntax is almost the same for all databases.

Where Is SQL Used, What Does It Do?

The main use of SQL is in databases, and it is needed to process the data stored in the database. It enables the data to be modeled within the targeted task definition.

Some software that does query work with SQL are as follows:

  • Microsoft SQL Server: It is a server-based software developed by Microsoft.
  • Oracle: Known as the most powerful database software and used in large companies and applications. Its developer is Oracle.
  • MSSQL: It is a paid software and written by Microsoft.
  • MySQL: It is free and open source software. Its developer is Oracle.
  • Access: Developed by Microsoft and preferred for smaller applications.

This list goes on and on.

What is a Database?

Today, it is necessary to keep the information in a place with primitive methods, to make transactions related to that information, to organize it, etc. Since it has become impossible, systems that systematically store countless data were needed. In order to store this much data, the concept of database has emerged.

A database is the area where data such as customer's personal information, account information or patient records of a hospital are stored in a bank with millions of customers. Databases provide data integrity, prevent data duplication.

Database applications are divided into:

  • Flat File Database: In these databases, all records must be kept in a single table. Therefore, data duplication is inevitable. For example, Excel and Word are databases of this type.
  • Relational Database: This is the part that we will be interested in. There are more than one table in this database and there is a relationship between the tables according to a certain hierarchy. MSSQL, Oracle, MySQL, PostgreSQL, Berkeley, Firebird, Sybase, Access are examples of relational databases.

What is Database Management System (DBMS)?

The systems that provide the management of works such as creating a database, adding new records, updating existing records are called Database Management System (DBMS). The purpose of the database management system is to facilitate software development, database management, performance measurements, and security by using the relevant database. DBYS provides communication and order between the database and the software that will use the database.

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