ruby on rails 3.2 - ActiveRecord include associations missing records -

i'm making following query

portfoliodistribution.joins(:portfolio_distribution_split).   select('policy_number, reinvestment_date, reinvestment_units,   reinvestment_units, split_name, split_percentage').   where(:policy_number => policy_no, :reinvestment_date => period,   :ods_psgamas_gls_portfolio_distribution_split => { :split_name => type }) 

which returns 15 records, associated model portfolio_distribution_split nil. if change query include associaterd model so:

portfoliodistribution.joins(:portfolio_distribution_split).   select('policy_number, reinvestment_date, reinvestment_units,   reinvestment_units, split_name, split_percentage').   where(:policy_number => policy_no, :reinvestment_date => period,   :ods_psgamas_gls_portfolio_distribution_split => { :split_name => type }).   includes(:portfolio_distribution_split) 

i 3 records? if take generated sql , run directly against database 15 records. happened other 12 records?

• activemodel (3.2.13)
• activerecord (3.2.13)
• activerecord-sqlserver-adapter (3.2.8)
• activeresource (3.2.13)
• activesupport (3.2.13)

my issue conceputal.

portfolio_distribution , portfolio_distribution_split have one-to-many relationship.

when run first query record each portfolio_distribution_split.

the second query returns record each portfolio_distribution array of portfolio_distribution_splits related portfolio_distributions