Create a Cumulative Sum Column in MySQL

Question

I have a table that looks like this:

id   count
1    100
2    50
3    10

I want to add a new column called cumulative_sum, so the table wou

Answer 1

You could also create a trigger that will calculate the sum before each insert

delimiter |

CREATE TRIGGER calCumluativeSum  BEFORE INSERT ON someTable
  FOR EACH ROW BEGIN

  SET cumulative_sum = (
     SELECT SUM(x.count)
        FROM someTable x
        WHERE x.id <= NEW.id
    )

    set  NEW.cumulative_sum = cumulative_sum;
  END;
|

I have not tested this