Databases are essential components in web development, allowing you to store, retrieve, and manage data efficiently. In this section, we will cover the basics of databases, focusing on relational databases, which are the most commonly used type in web applications.

1. Database: A structured collection of data that can be easily accessed, managed, and updated.
2. Relational Database: A type of database that stores data in tables, which are organized into rows and columns.
3. Table: A collection of related data entries consisting of rows and columns.
4. Row: A single record in a table.
5. Column: A field in a table; all rows in a table have the same columns.
6. Primary Key: A unique identifier for each record in a table.
7. Foreign Key: A field in one table that uniquely identifies a row of another table, creating a relationship between the two tables.
8. SQL (Structured Query Language): A standard language for managing and manipulating databases.

Some popular RDBMS include:

• MySQL
• PostgreSQL
• SQLite
• Microsoft SQL Server
• Oracle Database

Here are some fundamental SQL commands you will use frequently:

• CREATE DATABASE: Creates a new database.
• CREATE TABLE: Creates a new table in the database.
• INSERT INTO: Adds new records to a table.
• SELECT: Retrieves data from one or more tables.
• UPDATE: Modifies existing records in a table.
• DELETE: Removes records from a table.

Let's create a simple database and a table to store user information.

• id INT AUTO_INCREMENT PRIMARY KEY: Creates an id column that auto-increments with each new record and serves as the primary key.
• username VARCHAR(50) NOT NULL: Creates a username column that can store up to 50 characters and cannot be null.
• email VARCHAR(100) NOT NULL: Creates an email column that can store up to 100 characters and cannot be null.
• created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP: Creates a created_at column that stores the timestamp of when the record was created, with a default value of the current timestamp.

1. Create a new database named school.
2. Create a table named students with the following columns:
   • student_id (Primary Key, Auto Increment)
   • first_name (VARCHAR, 50 characters, Not Null)
   • last_name (VARCHAR, 50 characters, Not Null)
   • email (VARCHAR, 100 characters, Not Null)
   • enrollment_date (TIMESTAMP, Default Current Timestamp)

• Forgetting to use the database: Always ensure you are using the correct database with the USE command before creating tables or inserting data.
• Not defining a primary key: Every table should have a primary key to uniquely identify each record.
• Incorrect data types: Choose appropriate data types for each column to ensure data integrity and efficient storage.

In this section, we introduced the basics of databases, focusing on relational databases and SQL commands. You learned how to create a database and a table, and you practiced these skills with a practical exercise. In the next section, we will dive deeper into connecting to a MySQL database using PHP.