What are the advantages and disadvantages of normalizing a database versus using string manipulation functions in SQL queries in PHP?

When working with databases in PHP, it is generally better to normalize the database structure rather than relying on string manipulation functions in SQL queries. Normalizing the database ensures data integrity, reduces redundancy, and improves query performance. On the other hand, using string manipulation functions in SQL queries can lead to inefficient queries, potential data inconsistencies, and difficulty in maintaining the database structure.

// Example of normalizing a database table
CREATE TABLE users (
    id INT PRIMARY KEY,
    username VARCHAR(50) NOT NULL,
    email VARCHAR(100) NOT NULL,
    password VARCHAR(255) NOT NULL
);

// Example of using string manipulation functions in SQL queries
$query = "SELECT * FROM users WHERE SUBSTRING(username, 1, 1) = 'A'";