nhibernate newbe问题......这里很容易

I'm new to nhibernate so this should be easy. I have a mapping file as below although I deleted some fields that aren't relevant to this question. The streamfields class contains a bag of fieldmappings. I want the join to be on field_no column but the sql that is sent is on the id field (str_fld_id") as seen below.I'm new to nhibernate so this should be easy. I