What are the advantages and disadvantages of using JOIN statements in SQL queries to merge data from multiple tables in PHP applications?

Using JOIN statements in SQL queries allows you to merge data from multiple tables in a single query, reducing the need for multiple queries and improving performance. However, JOINs can also make queries more complex and harder to read, especially when dealing with multiple tables and conditions. It is important to carefully consider the type of JOIN (e.g. INNER JOIN, LEFT JOIN) to use based on the relationship between the tables and the desired result.

$query = "SELECT t1.column1, t2.column2
          FROM table1 t1
          INNER JOIN table2 t2 ON t1.id = t2.id";
$result = mysqli_query($connection, $query);
if(mysqli_num_rows($result) > 0) {
    while($row = mysqli_fetch_assoc($result)) {
        // Process the merged data
    }
} else {
    echo "No results found.";
}