根据先前行循环上的计算更新行

Question

I want to update the rows the rows of different person that has wrong amount.

Num | Name| Date Paid  | pay |old | new
1   | jon | 2014-08-01 | 100 |150 | 250
2   | jon | 2014-08-02 | 50  |250 | 300
3   | jon | 2014-08-03 | 110 |300 | 410
4   | jon | 2014-08-07 | 60  |410 | 470
5   | jon | 2014-08-09 | 200 |410 | 470
6   | jon | 2014-08-10 | 10  |410 | 470
7   | jon | 2014-08-15 | 100 |410 | 470
8   | jon | 2014-08-17 | 20  |410 | 470

sample database is here

The formula to get the amount of column(new) is that in the first date which is the number 1 is column(pay) + column(old) = column(new):

100+150 = 250. 

then the 250 will be put in the second row in column in Old then so on.

column(pay) + column(old) = column(new): 50 + 250 = 300. 

I want to update all the data that is wrong. Is there a way to update it will for loop or anything? there are about 400+ data that is wrong thanks for your time and help... :D

The formula of column(old) is the value of previous column(new) so the row number 5 - 8 has wrong data the column(old) and column(new) is there a way to update it continuesly?

Answer 1

You can do this with this statement:

UPDATE
    person p
INNER JOIN (
    SELECT
        p1.*, 
        p2.personID as p2id, 
        p2.oldpaidamount as old2, 
        p2.newpaidamount as new2
    FROM
        person p1
    INNER JOIN 
        person p2
    ON
        p1.personID > p2.personID
    AND
        p1.personName = p2.personName
    AND
        p2.personID = (
            SELECT 
                MAX(p3.personID)
            FROM
                person p3
            WHERE
                p3.personID < p1.personID
        )
    ) temp
ON
    p.personID = temp.personID
AND
    p.personName = temp.personName
SET
    p.newpaidAmount = temp.new2 + p.paidamount,   -- add this line to correct the newpaidamount
    p.oldpaidAmount = temp.new2
WHERE
    p.oldpaidAmount <> temp.new2

We materialize our subselect on the same table to avoid the restriction of MySQL that one cannot update a table while selecting from the same in a subselect. I use an INNER JOIN to get the desired value, because the first row doesn't need to be updated.

See it working in the modified fiddle .

Note:
You can't use an UPDATE trigger to keep this current, because an UPDATE trigger would trigger itself, so you should do updates with a stored procedure. For INSERT operation you could use a BEFORE INSERT trigger to get the correct value of OldpaidAmount.

I had the impression that both columns are redundant, if the whole history of paidamounts is stored (here's the start one with 150 missing).

Answer 2

    for($i=1;$i<=$totalnumberRows;$i++)
{

$mysqlUpdate = mysqli_query($con, "UPDATE
    person p
INNER JOIN (
    SELECT
        p1.*, 
        p2.personID as p2id, 
        p2.paidamount as paid2, 
        p2.oldpaidamount as old2, 
        p2.newpaidamount as new2
    FROM
        person p1
    INNER JOIN 
        person p2
    ON
        p1.personID > p2.personID
    AND
        p1.personName = p2.personName
    AND
        p2.personID = (
            SELECT 
                MAX(p3.personID)
            FROM
                person p3
            WHERE
                p3.personID < p1.personID 
                AND p3.personName = 'jon'
        )
    WHERE p1.personName = 'jon'

    ) temp
ON
    p.personID = temp.personID
AND
    p.personName = temp.personName
SET
    p.oldpaidAmount = temp.new2,
    p.newpaidAmount = temp.new2 + p.paidAmount");

}

The totalnumberRows will loop on how many times it will update until the last of the rows.. Credits to @VMai

Here is the code in sqlfiddle LINK!! It has a lot of Update query because i do not now how to loop in sqlfiddle but in php you can use forloop to do that thanks...