with v(bid, dt, uid)

as

(

select 34 as bid, '20150401' as dt, 'a'

union all select 35, '20150402', 'a'

union all select 36, '20150402', 'b'

union all select 37, '20150403', 'a'

union all select 38, '20150404', 'c'

)

select v1.*, (select count(*) as cnt from v where v.uid = v1.uid and v.dt < v1.dt) as cnt

from v v1

;