count the number of times patient 65759 had been tested for urea nitrogen in 07/2105.
select count(*) from labevents where labevents.itemid in ( select d_labitems.itemid from d_labitems where d_labitems.label = 'urea nitrogen' ) and labevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 65759 ) and strftime('%y-%m',labevents.charttime) = '2105-07'