Question

I would like to compare a date entered in a search field (e.g., 04.07.2012) with a date from my table (a datetime column called date). However, I can’t seem to get my SQL query straight.

What I tried:

find(:all, :conditions => ['\'to_timestamp(date, \'DD Mon YYYY\')\' LIKE \'to_timestamp(?, \'DD Mon YYYY\')\'', '#{query}']) 

but it fails:

PG::Error: ERROR:  syntax error at or near "DD"
LINE 1: ...s".* FROM "projects"  WHERE ('to_timestamp(date, 'DD Mon YYY...
                                                             ^
: SELECT "pacients".* FROM "projects"  WHERE ('to_timestamp(date, 'DD Mon YYYY')' LIKE 'to_timestamp('#{query}', 'DD Mon YYYY')')

I’m a real novice as far as (postgre)SQL is concerned and I would really appreciate some hints in the right direction of writing this query.

Thanks a million!

Answer 1

As meager pointed out there are a couple of issues here:

• incorrect string interpolation
• making the database do more work than necessary and using LIKE when you can do date searching more directly:

Let ActiveRecord format the date inputs use straight SQL to compare the dates, something like:

start_date = Date.civil(2012, 7, 4)
end_date = Date.civil(2012, 7, 20)
User.where(["date BETWEEN ? AND ?", start_date, end_date])

Converting the source date and the dates in the database to a timestamp formatted like a string and then using LIKE is very round-about and poor performing as well.