MySql嵌套选择与结果相同的表

Question

I'm trying to do nested mysql query but I'm failing it's as simple as I have a table called 'todo' which is for saving to-do list when I do well this code is just to show how I wanna do it logically , I know it doesn't work and I think it probably needs JOIN or UNION but I couldn't do it

$result = mysqli_query($con,"SELECT type FROM todo WHERE user = '$username' GROUP BY type");

while($row = mysqli_fetch_array($result))
{
    echo '<td>- <a href="list.php?type='.$row['type'].'">'."  ".$row['type'].'</a></td>';
    echo "</br>";

    $result2 = mysqli_query($con,"SELECT titleFROM todo WHERE type= '$row['type']'");
    while($row = mysqli_fetch_array($result2))
    {
        echo '<td>-- <a href="todo.php?type='.$row['title'].'">'."  ".$row['title'].'</a>
    }
</td>';
echo "</br>";
}

I want the result to like -Work --Mr Jack --Company -School --Android Class --Entrepreneurship --php development

and so on...

Answer 1

Your inner loop overwrites the outerloop's $row variable. Try using a different variable name in the inner loop. Also, there's an error in your inner loop's SQL query (missing space between the tablename and FROM keyword).