Running total over date range - fill in the missing dates

Question

I have the following table.

DATE  | AMT
10/10 | 300
12/10 | 300
01/11 | 200
03/11 | 100

How do I get the monthly total? A result like -

Answer 1

You can also generate a range on the fly, pass its value as the interval to DATE_ADD, and basically project a sequence of month values.

As @Dems said, you need to have a correlated subquery calculate the running total, which will be very inefficient, because it will run a nested loop internally.

To see how to generate the sequence, check my post here: How to generate a range of numbers in Mysql

The end query should look something like this: (Incidentally, you should have a date column, not this varchar mess).

/*NOTE: This assumes a derived table (inline view) containing the sequence of date values and their corresponding TOT value*/
SELECT
  DATEVALUES.DateValue,
  (
  SELECT SUM(TABLE1.AMT) FROM TABLE1 WHERE TABLE1.DateValue <= DATEVALUES.DateValue)
  ) AS RunningSubTotal
FROM
  DATEVALUES

Or something like that.