计算数据库中30天以内，30-60天，60-90天，90天以外的数据的个数（用sql实现）

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