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我想要计算一个特定学生在一个特定的月份中离开MySQL数据库中的离开表离开的离开。我使用的代码 -Rails:在一个循环中调用一个函数为每次迭代返回相同的值
def calculate(student_id)
leave = Leave.find_by_sql("SELECT leave_duration FROM leaves WHERE MONTH(leave_from) = 2
AND YEAR(leave_from) = 2013 AND MONTH(leave_to) = 2 AND YEAR(leave_to) = 2013 AND
academic_status = 'APPROVED' AND warden_status = 'APPROVED' AND student_id = student_id
AND status = 'ACTIVE'")
sum = leave.sum(&:leave_duration)
return sum
end
----------更新的以下摘录----------
def calculate(student_id)
sum = Leave.find_by_sql("SELECT leave_duration FROM leaves WHERE MONTH(leave_from) = 2
AND YEAR(leave_from) = 2013 AND MONTH(leave_to) = 2 AND YEAR(leave_to) = 2013 AND
academic_status = 'APPROVED' AND warden_status = 'APPROVED' AND student_id = student_id
AND status = 'ACTIVE'").sum(&:leave_duration)
return sum
#it did the trick for me.
end
上述方法计算在2013年2月份的某个学生留下的留下余额,并将叶子的总和返回到调用函数。
def calcuateLeaveForEachStudent
array = Leave.find_by_sql("select student_id from students")
c = Array.new
for i in 0...array.length
student_id = array[i].student_id
c[i] = calculate(student_id)
end
end
但是当我调用上述方法时,'calculate'方法在每次迭代时返回相同的值。这可能是什么可能的解决方案..?提前致谢..!
PS -
代码在Rails控制台上完美运行,没有任何语法错误,但存在一些我无法弄清楚的错误。
正确的方法是计算(操作,列名,选项= {})。你的方法就像计算(总和,student_id) – 2013-02-21 06:56:13
更好的选择将使用find选项而不是find_by_sql! – 2013-02-21 06:58:49
@SachinR你会详细说明一下吗?我只是不明白..! – 2013-02-21 07:04:47