SQL-Basics

What does SQL stand for?

Structured Query Language

For what is SQL used?

SQL is a standard language for manipulating data held in relational database management systems or for stream processing in relational data stream management systems.

What is a RDBMS?

A Relational Database Management System (RDBMS) is software that manages data stored in relational databases, allowing for data creation, querying, updating, and administration.

Who first developed SQL?

It was first developed in the 1970s by IBM.

Which components are there in SQL?

Queries, Data Definition Language (DDL), Data Manipulation Language (DML), Data Control Language (DCL), and Transaction Control Language (TCL).

Queries

This is the component that allows you to retrieve data from a database. The SELECT statement is most commonly used for this purpose.

Data Definition Language (DDL)

It lets you to create, alter, or delete databases and their related objects like tables, views, etc. Commands include CREATE, ALTER, DROP, and TRUNCATE.

Data Manipulation Language (DML)

 It lets you manage data within database objects. These commands include SELECT, INSERT, UPDATE, and DELETE.

Data Control Language (DCL)

It includes commands like GRANT and REVOKE, which primarily deal with rights, permissions and other control-level management tasks for the database system.

What are relational databases?

Relational databases are a type of database management system (DBMS) that stores and provides access to data points that are related to one another. They use a structure that allows data to be organized into tables with rows and columns.

What are key features of a relational database?

• use of SQL for querying and managing data

• support of ACID transactions (Atomicity, Consistency, Isolation, Durability)

• enforcement of data integrity through constraints

• ability to establish relationships between tables, enabling complex queries and data retrieval

• scalabilty and support for multi-user environments

Examples for popular relational database systems

MySQ, PostgreSQL, Oracle and Microsof SQL Server