What are the potential pitfalls of using multiple tables in MySQL queries for a tagging system in PHP?

When using multiple tables in MySQL queries for a tagging system in PHP, potential pitfalls include increased complexity of queries, slower performance due to joins, and potential data redundancy. To solve this issue, consider using a single table for storing tags and their relationships to the tagged items, which can simplify queries and improve performance.

// Example of creating a single table for tags and their relationships
CREATE TABLE tags (
    id INT PRIMARY KEY AUTO_INCREMENT,
    tag_name VARCHAR(50) NOT NULL
);

CREATE TABLE tagged_items (
    id INT PRIMARY KEY AUTO_INCREMENT,
    item_name VARCHAR(50) NOT NULL
);

CREATE TABLE tag_relationships (
    tag_id INT,
    item_id INT,
    PRIMARY KEY (tag_id, item_id),
    FOREIGN KEY (tag_id) REFERENCES tags(id),
    FOREIGN KEY (item_id) REFERENCES tagged_items(id)
);