Mysql syntax error when trying to capture cumulative sum

Rails
1

Hey all,

I’ve searched the web and cannot find an example of getting a cumulative
count by month for a specific object using Rails, and then displaying
that in an array. This gives a mysql syntax error:

count = Student.count("SELECT
    x1.MonthNo
  , x1.MonthName
  , x1.Added
  , SUM(x2.Added) AS RunningTotal
  FROM
  (
  SELECT
    MONTH(passed_on) AS MonthNo
  , MONTHNAME(passed_on) AS MonthName
  , COUNT(*) AS Added
  FROM students
  WHERE passed_on >= '2009-09-23'
  GROUP BY MONTH(passed_on)
  ) AS x1
  INNER JOIN (
  SELECT
    MONTH(passed_on) AS MonthNo
  , MONTHNAME(passed_on) AS MonthName
  , COUNT(*) AS Added
  FROM students
  WHERE passed_on >= '2009-09-23'
  GROUP BY MONTH(passed_on)
  ) AS x2
  ON x1.MonthNo >= x2.MonthNo
  GROUP BY x1.MonthNo;")

def panels
:series => [{
:name => ‘Passed’,
:data => count
}
end

The idea is to show the cumulative sum over several months which will be
displayed in a chart. Thanks for any response.

2

On Apr 6, 12:19 am, John M. [email protected] wrote:

Hey all,

I’ve searched the web and cannot find an example of getting a cumulative
count by month for a specific object using Rails, and then displaying
that in an array. This gives a mysql syntax error:

count is expecting a rather simpler situation. If you’re supplying a
full sql statement you should use count_by_sql (and you might actually
want to use connection.select_all in this case).

Fred

3

Frederick C. wrote:

On Apr 6, 12:19�am, John M. [email protected] wrote:

Hey all,

I’ve searched the web and cannot find an example of getting a cumulative
count by month for a specific object using Rails, and then displaying
that in an array. This gives a mysql syntax error:

count is expecting a rather simpler situation. If you’re supplying a
full sql statement you should use count_by_sql (and you might actually
want to use connection.select_all in this case).

Fred

Initially, I felt this would be more efficient:

def sum
a = Student.passed_on
a.inject(0) { |s,v| s += v }

end

But this gives me undefined method “passed_on” and undefined method
“inject”.