问SQL Server查询日期范围之间一个月的总天数

EN

  select dateadd(m,datediff(m, 0, d.thedate),0) themonth, count(1)
    from dates d
    join ranges r on d.thedate between r.[from date] and r.[to date]
group by datediff(m, 0, d.thedate)
order by themonth;

|   themonth | COLUMN_1 |
-------------------------
| 2012-11-01 |        9 |
| 2012-12-01 |        1 |

;with dates(thedate) as (
  select dateadd(yy,years.number,0)+days.number
    from master..spt_values years
    join master..spt_values days
      on days.type='p' and days.number < datepart(dy,dateadd(yy,years.number+1,0)-1)
   where years.type='p' and years.number between 100 and 150
      -- note: 100-150 creates dates in the year range 2000-2050
      --       adjust as required
)
  select dateadd(m,datediff(m, 0, d.thedate),0) themonth, count(1)
    from dates d
    join ranges r on d.thedate between r.[from date] and r.[to date]
group by datediff(m, 0, d.thedate)
order by themonth;

select ((day(date_to)) - (day(date_from))) as no_of_days,month(date_from)as month from tablename 

CREATE TABLE dateData
    (fromdate datetime, todate datetime)
;

INSERT INTO dateData
    (fromdate, todate)
VALUES
    ('2012-11-10', '2012-11-15'),
    ('2012-11-21', '2012-11-22'),
    ('2012-11-30', '2012-12-01')
;

select mth, sum(days) as daysInMth
from
(
select month(fromdate) as mth,
sum(case 
when month(fromdate) = month(todate) then datediff(dd, fromdate, todate)+1
else datediff(dd, fromdate, dateadd(mm, 1, fromdate) - day(fromdate)) + 1 end)
as days 
from dateData
group by month(fromdate)
union
select month(todate) as mth,
sum(case when month(todate) <> month(fromdate) then
datediff(dd, fromdate, dateadd(mm, 1, fromdate) - day(fromdate)) + 1
else 
case when month(todate) = month(fromdate) then 0 else
datediff(dd, convert(datetime, year(todate) + '-' + month(todate) + '-1'), todate) 
end
end) as days
from dateData
group by month(todate)
) aggregated
group by mth