UPDATE supplier
SET dbcr = CASE 
              WHEN dbcr = '1' THEN 'Credit'
              WHEN dbcr = '2' THEN 'Debit'
           END
WHERE dbcr IN ('1','2');

UPDATE Customer
SET dbcr = CASE 
              WHEN dbcr = '1' THEN 'Debit'
              WHEN dbcr = '2' THEN 'Credit'
           END
WHERE dbcr IN ('1','2');