您无法在MySQL的FROM子句中指定要更新的目标表

Question

I want to change the status of a single order by selecting its requisition_id where the status matches a specific keyword. But it keeps showing me this error "You can't specify target table for update in FROM clause"

UPDATE order_info
SET status ='Approved' 
WHERE requisition_no IN (SELECT requisition_no FROM order_info WHERE status = 'not approved')

What can I do to fix it?

EDIT- I've included the PHP code as well

while ($row = mysqli_fetch_array($result)){
echo "<tr>";
    echo "<td>" . $row['requisition_no'] . "</td>";
    echo "<td>" . $row['desig'] . "</td>";
    echo "<td>" . $row['deptt'] . "</td>";
    echo "<td>" . $row['type'] . "</td>";
    echo "<td>" . $row['make'] . "</td>";
    echo "<td>" . $row['quantity'] . "</td>";
    echo '<form method="post" action="status.php">'; /*Redirects to status.php to change the status (using diff. page because i'm a hopeless kid, who doesnt want to learn new ways of simplifying things)*/
    echo "<td>" . $row['status'] . "<br/>";

    if($row['status']=='Approved' || $row['status']=='Under Procurement'){//does nothing
    }
            /*Here, using a submit button*/
    else { echo '<input type="submit" name="status" value="Approve"></td>';
    $_SESSION['rno'] = $row['requisition_no'];}
    echo '</form>';

Answer 1

You have a few syntax errors probably causing this error. You are missing an equals sign = after status and the right parenthesis ) at the end:

UPDATE order_info o
SET o.status = 'Approved' 
WHERE o.requisition_no IN (SELECT x.requisition_no FROM (select * from order_info) x WHERE x.status = 'not approved')

Also, I think your query can be rewritten like this:

UPDATE order_info
SET status = 'Approved' 
WHERE status = 'not approved'