What is the potential issue with using DISTINCT in a SQL query when dealing with multiple table joins in PHP?

When using DISTINCT in a SQL query with multiple table joins in PHP, it may not work as expected because it eliminates duplicate rows based on all selected columns. This can be problematic when joining multiple tables as it may remove valid duplicates that are needed for the query results. To solve this issue, you can use GROUP BY instead of DISTINCT, which allows you to group the results by specific columns while still including all necessary data.

$query = "SELECT column1, column2, column3
          FROM table1
          JOIN table2 ON table1.id = table2.id
          GROUP BY column1, column2, column3";
$result = mysqli_query($connection, $query);

if ($result) {
    while ($row = mysqli_fetch_assoc($result)) {
        // Process the results
    }
} else {
    echo "Error: " . mysqli_error($connection);
}