Question

I have a table date, subs, unsubs, where date is PK, and subs and unsubs are the number of subscribes and unsubscribes on that date.

I want to add a column to calculate the number of total subscribers on each day, that is, if sort date, subsall = subsall of last row + subs – unsubs.

For example: the table is

----------------
2012-01-01, 5, 2
2012-01-02, 6, 1
2012-01-03, 4, 3
----------------

I want to add a new column and the table becomes

-------------------
2012-01-01, 5, 2, 3
2012-01-02, 6, 1, 8
2012-01-03, 4, 3, 9
-------------------

What is the MySQL command to do that?

Answer 1

You are looking for a cumulative sum. Try this:

SELECT date, subs, unsubs, (@csum := @csum + subs - unsubs) cumulative
FROM table, (SELECT @csum :=0) c
ORDER BY date