Question

Im using mysql and This is the entry I have in my current table.

So here previous balance for current month should be the remaining balance of previous month. How do I get this value from previous row of database.

Previous_balance Remaining_Balance
        0.00        42.64
        0.00        627.69
        0.00        45.54
        0.00        67.60

The result should be

Previous_balance Remaining_Balance
        0.00        42.64
        42.64       627.69
        627.69      45.54
        45.54       67.60

I have ID as PK and I want store the new previous_balance in database and print on form. So I can calculate Monthly charges and usage and other stuff. Thanks for answers.

Answer 1

On the assumption that the id field is ordered, try this:

UPDATE Balances 
  SET b1.Previous_balance = COALESCE((SELECT b2.Remaining_Balance 
                                      FROM Balances b2 
                                      WHERE b2.id < b1.id 
                                      ORDER BY b2.id DESC 
                                      LIMIT 1),0) 
FROM Balances b1

I don’t have an installation of mySQL, so I can’t vouch for all the syntax. I know the SELECT statement works though.