如何使用具有动态值的变量更新sql表

Question

I have a php code which sums up the value of the same column from two different tables of same database and stores it in a variable. The code is mentioned below:

$sql = 'SELECT
        (SELECT SUM( time_spent )
         FROM '.TICKET_RESPONSE_TABLE.'
         WHERE ticket_id='.db_input($id).')
        +(SELECT SUM( time_spent )
          FROM '.TICKET_NOTE_TABLE.'
          WHERE ticket_id='.db_input($id).')
    AS total_time';
$result = db_query($sql);
$cursor = mysql_fetch_row($result);
$total_time = $cursor[0];

Now,I want is to update a column in another table of the same database, with the value stored in the variable $total_time. Kindly help me with the same.

Answer 1

You can make a subselect:

UPDATE table1 t1
SET t1.val1 =
(SELECT val FROM table2 t2 WHERE t2.id = t1.t2_id )
WHERE t1.val1 = '';