what is the daily average phosphate level of patient 51663 until 2 months ago?
select avg(labevents.valuenum) from labevents where labevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 51663 ) and labevents.itemid in ( select d_labitems.itemid from d_labitems where d_labitems.label = 'phosphate' ) and datetime(labevents.charttime) <= datetime(current_time,'-2 month') group by strftime('%y-%m-%d',labevents.charttime)