Dealing with different datetime formats in the DB? - mysql

Question

I'm writing a Ruby program using Sequel which is running on the legacy database. There is an issue dealing with different date time formats.
DB has a table which has a column start_date. In Sequel's migration script I set it to DateTime which is a timestamp type in SQLite, however, the legacy data has a different time format:
Some are using an ISO8601, like 2013-09-01T08:28:00+10:00.
Some are using a different one, which I don't know if it has a name, like 2013-09-01 08:28:00.000000+1000.
The problem is, when I run a query against the table and try to filter by start_date, the difference between two date time formats will cause incorrect results.
The query I'm using is:
current = Time.now
MyModel.where { start_date < current }
Sequel will convert it into SQL like this:
SELECT * FROM `my_model` WHERE `start_date` < '2013-09-01 08:28:00.000000'
From my local testing, Sequel looks like it's comparing the date as a string, so 2013-09-01 08:28:00.000000+1000 is less than 2013-09-01T01:28:00+10:00. Because whitespace is less than T this is not what I want.
I could use an iso8601 time like:
current_iso8601 = Time.now.iso8601
MyModel.where { start_date < current_iso8601 }
But it won't solve the problem because the database has two different datetime formats.
My questions are:
Does Ruby/Sequel support querying the database by Date/Time not as a string?
Does it work for different date time formats?
SQLite is just for local testing, in production it will be MySQL. So, the solution should be using general Sequel methods as a adaptor and should not have any database specific methods.
NOTE: the program is not a Rails application.
Thank you very much!

Answer 1

SQLite does not have date/time types (see http://sqlite.org/datatype3.html). It stores datetime values as strings.
The best solution is to use the same database in development/testing that you use in production. If you don't want to do that, you need to convert all the SQLite datetime values so that they all use the same ISO8601 format. That way the comparison operators will work correctly (as they do in MySQL).