What are the advantages and disadvantages of using multiple MySQL queries versus optimizing queries for efficiency in PHP scripts?

When working with MySQL databases in PHP scripts, it is important to consider the trade-offs between using multiple queries and optimizing queries for efficiency. Using multiple queries can make the code easier to read and maintain, but it may result in slower performance due to the overhead of making multiple database connections. On the other hand, optimizing queries for efficiency can improve performance by reducing the number of database calls, but it may make the code more complex and harder to understand.

// Using multiple queries approach
$query1 = "SELECT * FROM users WHERE role = 'admin'";
$result1 = mysqli_query($conn, $query1);

$query2 = "SELECT * FROM orders WHERE user_id = 1";
$result2 = mysqli_query($conn, $query2);

// Optimizing queries for efficiency approach
$query = "SELECT users.*, orders.* FROM users 
          INNER JOIN orders ON users.id = orders.user_id 
          WHERE users.role = 'admin' AND users.id = 1";
$result = mysqli_query($conn, $query);