Question

I have a table called payment which adds all the payment entries. I have field in payment table as customer_id which refers to the customer id in the customer table.

There is a field called flag where I store 1 or 0 based on their payment status. If they paid the full amount they flag will be 0 and if there is a balance the flag wil be 1

There is another field in payment table, added_on, which is a timestamp

I want to fetch out the latest added row of all the customer_id(in the payment table) who have flag 1(pending payment)

I tried fetching from the payment table like this

   $rResult = mysql_query("select * from payment  where flag='1'")

and then looped like this

    while ($aRow=mysql_fetch_object($rResult))
        {
        //fetch out the customer id like this
$customer= $aRow->customer_id;
    $pay_quer = mysql_query("select*from payment where customer_id='$customer'");

        } 

I know it is long to do this..is there any shorter way to do it with one query?
The results are not coming as I expected too. 🙁

Answer 1

SELECT p.* 
FROM 
    payment AS p
  JOIN
    ( SELECT customer_id
           , MAX(added_on) AS max_added_on
      FROM payment
      WHERE flag='1'
      GROUP BY customer_id
    ) AS g
    ON  g.customer_id = p.customer_id
    AND g.max_added_on = p.added_on
ORDER BY p.added_on DESC

or (it’s not clear what you want exactly nor how the flag is used). This will show different results, only those customers that their latest row in the payment has flag=1:

SELECT p.* 
FROM 
    payment AS p
  JOIN
    ( SELECT customer_id
           , MAX(added_on) AS max_added_on
      FROM payment
      GROUP BY customer_id
    ) AS g
    ON  g.customer_id = p.customer_id
    AND g.max_added_on = p.added_on
WHERE p.flag='1'
ORDER BY p.added_on DESC