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Update next line if current updated line is 0

My table looks like this:

HarvestID  |  CheckIn | Actual | Status
1          |   Date   | 100    | Process
2          |   Date   | 200    | Process
3          |   Date   | 400    | Process

and my problem is how to update the following line if I set the value Qty = '350' and then update the id '1' and '2' to 0 and ID '3' Qty = '350'

Is there a way to do this without forcing the new table to stock the sum of "A" and using a stored procedure?

I am already trying:

    cmdTemp = New MySqlCommand("SELECT * FROM tb_harvest ORDER BY CheckIn ASC LIMIT 1", cn)
    sqlrd = cmdTemp.ExecuteReader
    While sqlrd.Read
        harvestid = sqlrd("HarvestID")
        qtyTemp1 = sqlrd("Actual") - Qty : qtyTemp2 = sqlrd("Actual")
    End While
    sqlrd.Close()
    If qtyTemp1 < 0 Then
        cmdTemp = New MySqlCommand("UPDATE tb_harvest SET Actual=0 WHERE HarvestID=" & harvestid & "; " & _
                                   "UPDATE tb_harvest SET Actual=Actual+" & qtyTemp1 & " WHERE HarvestID=" & harvestid + 1, cn)
        cmdTemp.ExecuteNonQuery()
    Else
        cmdTemp = New MySqlCommand("UPDATE tb_harvest SET Actual=Actual-" & qtyTemp2 & " WHERE HarvestID=" & harvestid, cn)
        cmdTemp.ExecuteNonQuery()
    End If
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1 answer


You can do it with variables:



set @qty = 350;

update tb_harvest
    set actual = (case when @qty <= 0 then 0
                       when @qty >= actual
                       then if(@qty := @qty - actual, 0, 0)
                       when (@tmp := actual - @qty),
                       then if(@qty := 0, @tmp, @tmp)
                       else actual -- should never happen
                  end)
    order by harvestid;
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