laurells/alx_database

Introduction to Databases and SQL

This repository provides a basic overview of databases, relational databases, SQL, and MySQL, along with essential concepts related to managing data using SQL.

What's a Database?

A database is a structured collection of data stored in a systematic manner for easy retrieval, modification, and management. It serves as a repository for various types of information, from simple data points to complex records.

What's a Relational Database?

A relational database is a type of database that stores data in tables, where each table represents a specific entity, and the relationships between entities are established using keys and indexes.

What Does SQL Stand For?

SQL stands for Structured Query Language. It is a programming language designed for managing and manipulating relational databases. SQL provides a standardized way to communicate with databases, enabling users to perform tasks like querying, updating, and managing data.

What's MySQL?

MySQL is an open-source relational database management system (RDBMS) that uses SQL as its querying language. It is widely used for various applications, from small-scale projects to large enterprise solutions.

Creating a Database in MySQL

To create a database in MySQL, you can use the CREATE DATABASE statement:

CREATE DATABASE database_name;

DDL and DML

• DDL (Data Definition Language) is used to define and manage the structure of the database, such as creating, altering, or dropping tables.
• DML (Data Manipulation Language) is used to manage the data within the database, including operations like inserting, updating, and deleting records.

Creating or Altering a Table

To create a table, use the CREATE TABLE statement:

CREATE TABLE table_name (
    column1 datatype,
    column2 datatype,
    ...
);

To alter a table, use the ALTER TABLE statement:

ALTER TABLE table_name
ADD column_name datatype;

Selecting Data from a Table

To retrieve data from a table, use the SELECT statement:

SELECT column1, column2
FROM table_name
WHERE condition;

Inserting, Updating, or Deleting Data

• To insert data, use the INSERT INTO statement:

INSERT INTO table_name (column1, column2)
VALUES (value1, value2);

• To update data, use the UPDATE statement:

UPDATE table_name
SET column1 = new_value1, column2 = new_value2
WHERE condition;

• To delete data, use the DELETE FROM statement:

DELETE FROM table_name
WHERE condition;

Subqueries

Subqueries are nested queries within other SQL queries. They allow you to retrieve data from one table based on values from another table.

Using MySQL Functions

MySQL provides a range of built-in functions for tasks like mathematical calculations, date and time manipulation, string operations, and more. Examples include SUM, COUNT, DATE_FORMAT, and CONCAT.

This repository serves as a starting point to understand the basics of databases, SQL, and MySQL. For more in-depth knowledge and practical experience, refer to relevant resources, tutorials, and documentation.