Comparison of time

rubyonrails-talk
1

Hello all,

I want to compare the below given times.

from_time = '08:00 am'

to_time = '04:30 pm'

@logtime = "ci.time >= '#{from_time}' and ci.time <= '#{@to_time}'"

but its not working fine...giving me the wrong results... Any other methods or how can i try with.. pls help me out

Thank you

2

As it stands, those variables are Strings, not Times (or DateTimes), and will be evaluated as strings in the SQL.

What values are you storing in the DB? Is it at Datetime format column?

3

Newb Newb wrote:

Hello all,

I want to compare the below given times.

from_time = '08:00 am'

to_time = '04:30 pm'

@logtime = "ci.time >= '#{from_time}' and ci.time <= '#{@to_time}'"

but its not working fine...giving me the wrong results... Any other methods or how can i try with.. pls help me out

Thank you

the below is my sample data of my date field

01:21:09 pm

4

my date field in the varchar datatype

Thank you for your time...

5

You're a little bit stuffed then - as comparing greater/less than is comparing strings not times...

You can fudge it in your queries (assuming MySQL) using the "str_to_date" function - but roll your sleeves up, as it's gonna be messy!

http://dev.mysql.com/doc/refman/5.1/en/date-and-time-functions.html#function_str-to-date

6

you can try distance_of_time_in_words_to_now… Read this http://apidock.com/rails/ActionView/Helpers/DateHelper/distance_of_time_in_words_to_now

Nitin.

7

my date field in the varchar datatype

I would suggest changing the fields to DateTime. Then you will be able to do direct comparisons.

Colin

8

Colin Law wrote:

I would suggest changing the fields to DateTime. Then you will be able to do direct comparisons.

From someone who has been burned by this in the past, I have a slightly different suggestion.

If you actually do need to store a time that is independent of a date, I would recommend storing time as an offset. Something like seconds from midnight. Store this value as an integer in the database.

Using such a technique eliminates dependency on the geo-political rules governing the representation of dates and times.

For convenience you could add an instance method to give you the time of day as a string.

# Assume the "time_offset" column contains 25000 (seconds from midnight) def presentable_time   t = Date.today.to_time + self.time_offset.seconds   t.strftime("%I:%M %p") end

puts my_object.presentable_time => "06:56 AM"

With this technique your "difference" or "duration" calculations become trivial:

time_diff_seconds = obj_1.time_offset - obj_2.time_offset

It's not that common that one needs to store time independently of date. However, one case that comes to mind would be if you were calculating statistics based on time of day. Maybe you would want a graph showing activity based on the time of day. If you're doing something like that then having the time of day stored separately from the date would simplify the queries.

select * from orders where time_offset between 46800 and 54000;

would select all orders placed between 1:00 PM and 3:00 PM