30天以内:select count(*) from TB where datediff(day,字段名,getdate()) between 0 and 30
30-60天:select count(*) from TB where datediff(day,字段名,getdate()) between 30 and 60
60-90天:select count(*) from TB where datediff(day,字段名,getdate()) between 60 and 90
90天以外:select count(*) from TB where datediff(day,字段名,getdate())>90