What are the differences in approach between beginner and advanced PHP developers when structuring database queries for displaying hierarchical data?

Beginner PHP developers may use simple queries to fetch hierarchical data from a database, resulting in multiple queries and inefficient code. Advanced PHP developers, on the other hand, may utilize recursive functions or common table expressions (CTEs) to efficiently retrieve and display hierarchical data in a single query. 

// Example of using recursive function to fetch hierarchical data
function fetchCategories($parent_id, $level = 0) {
    $query = "SELECT * FROM categories WHERE parent_id = $parent_id";
    $result = mysqli_query($connection, $query);

    while ($row = mysqli_fetch_assoc($result)) {
        echo str_repeat('-', $level) . $row['name'] . "<br>";
        fetchCategories($row['id'], $level + 1);
    }
}

// Call the function to display hierarchical categories
fetchCategories(0);

Keywords

SQL queries Recursive functions Nested sets Parent-child relationships Tree structures

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