I have a table(currentbalance) that needs to be updated every month, the columns I need are Customer and balance, if customer didn't earn any balance I want to keep their current balance in tact but update any other customers balance that has changed. I've tried the "update" function but not working. Any direction appreciated.

SELECT a.customer, sum(a.redeem) as redeemed;
  FROM redeem a, date b;
  WHERE a.date between b.startdate AND b.enddate;
    group BY a.customer;
    into CURSOR redemption

SELECT customer, VAL(points) as Points;
  FROM ag;
  INTO cursor Pts

SELECT customer, sum(points) as Points;
  FROM pts;
  GROUP BY customer;
  INTO CURSOR CurtPts

SELECT a.customer, (b.balance-a.redeemed)+ c.points as Balance;
 FROM redemption a, currentbalance b, curtPts c;
 WHERE a.customer=b.customer AND c.customer=a.customer;