Databases, Tables, Columns, Data Types, and Schema Basics

What a Database and Table Mean

A database is a named container for related tables and other objects. A table stores rows of records, while columns define the shape of each record. This structure is the core of relational data design.

A Simple Table Example

CREATE TABLE students (
    id INT PRIMARY KEY AUTO_INCREMENT,
    name VARCHAR(100) NOT NULL,
    email VARCHAR(255) UNIQUE,
    enrolled_on DATE
);

This example shows column types, primary key usage, nullability, and uniqueness rules.

Common Data Types

• INT for integer values
• VARCHAR for variable-length strings
• TEXT for larger textual content
• DATE and DATETIME for time-related values
• DECIMAL for precise financial amounts
• BOOLEAN or tiny integer style fields for yes/no state

Why Data Type Choice Matters

Good type selection affects storage, performance, clarity, constraints, and application correctness. Financial numbers, for example, should usually avoid floating types where exact precision matters.

Business Example

An employee table might store employee ID, full name, department, joining date, salary, and status flags. Schema design makes those business concepts explicit and queryable.