是不是可以这样, 没测试哈 -
select a.NI
from PatientAdmissionsData a join PatientAdmissionsData b
on b.NI = a.NI and
b.AdmissionDate > a.AdmissionDate and b.AdmissionDate < dateadd(m, 2, a.AdmissionDate)
group by a.NI, a.AdmissionDate
having count(*) > 5
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本帖最后由 png 于 2012-6-7 11:37 编辑 ]