Question

I have 3 tables & models:
brands
brand_data_records
and
brand_data_records_brands – the join table

In rails i want all brand_data_records for a given date range for a given brand where a given attribute is not null in the db.

So I have:

BrandDataRecord.find(:all, :select => column_match, :joins => :brands, :conditions => ["brand_data_records_brands.brand_id = ? and date_retrieved >= ? AND date_retrieved <= ? and ? IS NOT NULL",brand.id,start_date,end_date,column_match])

This generates this sql:

  SELECT sentiment FROM `brand_data_records` INNER JOIN `brand_data_records_brands` ON `brand_data_records_brands`.brand_data_record_id = `brand_data_records`.id INNER JOIN `brands` ON `brands`.id = `brand_data_records_brands`.brand_id WHERE (brand_data_records_brands.brand_id = 330516084 and date_retrieved >= '2011-05-02' AND date_retrieved <= '2011-06-01' and 'sentiment' IS NOT NULL) 

Which generally works, but it gives back a bunch of extra records that have a null value. I think its something to do with the joins, if I remove them with sql only it works fine, but im not sure how to fix in rails (or even in sql for that fact)

Answer 1

You probably mean to reference the column:

 `sentiment` IS NOT NULL

What you’re doing inadvertently is asserting that the string 'sentiment' is not null, which of course it will never be. Passing in :sentiment or 'sentiment'.to_sym' in your conditions should fix this as symbols get escaped with backquotes on conversion.