PHP & MySQL · Lesson 1 of 11

Introduction to MySQL

Understand tables, rows, columns, keys, and relational data.

Lesson

MySQL is a relational database that stores records in tables with defined columns. A primary key identifies a row; foreign keys relate rows between tables. Design columns with suitable types and constraints, and use migrations to track schema changes reproducibly. The sample schema models one user with a unique email address. Further guidance Use migrations to version schema changes, constraints to protect relationships, and prepared statements for every dynamic value. Scope writes with a precise condition, check affected rows, and use transactions when multiple statements must succeed together. Store credentials outside source control. Practice task: Create a fresh example for Introduction to MySQL. Predict the result before running it, then change one input and explain why the result changes. Test a normal case and one boundary or invalid case where it applies. Compare your output with the example and note one rule you would use in a real project.

Code examples

SQL

CREATE TABLE users (
    id BIGINT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
    email VARCHAR(255) NOT NULL UNIQUE
);

Expected output

A users table with a unique email constraint

Key points

Understand tables, rows, columns, keys, and relational data.
Use prepared statements for values and constraints for data integrity.
Scope writes carefully and verify their result.

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