What are the differences between using a LEFT JOIN and an inner loop in PHP queries, and when should each method be used?

When using a LEFT JOIN in PHP queries, all records from the left table are returned, along with matching records from the right table. If there are no matches, NULL values are returned for the right table columns. On the other hand, an inner join only returns records that have matching values in both tables. LEFT JOIN should be used when you want to retrieve all records from the left table, even if there are no matches in the right table. Inner join should be used when you only want to retrieve records that have matching values in both tables.

// Using LEFT JOIN
$query = "SELECT * FROM table1 LEFT JOIN table2 ON table1.id = table2.id";
$result = mysqli_query($connection, $query);

// Using INNER JOIN
$query = "SELECT * FROM table1 INNER JOIN table2 ON table1.id = table2.id";
$result = mysqli_query($connection, $query);