计算周

Question

数我所说的表日历和数据的模样：

Date       Week_Num  Month_Year 
1996-01-27 00:00:00.000  1021   01/1997 
1996-01-28 00:00:00.000  1021   01/1997 
1996-01-29 00:00:00.000  1021   01/1997 
1996-02-03 00:00:00.000  1022   01/1997 
1996-02-04 00:00:00.000  1022   01/1997 
1996-02-10 00:00:00.000  1023   01/1997 
1996-02-11 00:00:00.000  1023   01/1997 

我要计算在MONTH_YEAR周数：

我写了类似的查询：

Select Month_year,Count(*) 
From (Select Week_Num,Month_year 
     From Calendar 
     Group By Week_Num,Month_year 
    )a 
Group By Month_year 
order by Month_year 

这是给我我想要什么，但有没有更好的方法呢？

Answer 1

SELECT Month_Year, COUNT(DISTINCT Week_Num) 
FROM Calendar 
GROUP BY Month_Year 

这可以删除一个级别的聚合并且更具可读性。不过，我不确定它是否会有更好的表现。

样品概念证明：

DECLARE @t table (DT smalldatetime, week_num int, month_year varchar(100)) 

INSERT INTO @t 
VALUES 
('1996-01-27 00:00:00.000', 1021,'01/1997'), 
('1996-01-28 00:00:00.000', 1021,'01/1997'), 
('1996-01-29 00:00:00.000', 1021,'01/1997'), 
('1996-02-03 00:00:00.000', 1022,'01/1997'), 
('1996-02-04 00:00:00.000', 1022,'01/1997'), 
('1996-02-10 00:00:00.000', 1023,'01/1997'), 
('1996-02-11 00:00:00.000', 1023,'01/1997') 

SELECT Month_Year, COUNT(DISTINCT Week_Num) 
FROM @t 
GROUP BY Month_Year 

返回：

Month_Year (No column name) 
01/1997   3 

Answer 2

我，这是你所需要的：

Select Month_year,Count(distinct Week_Num) 
From Calendar 
Group By Month_year 
order by Month_year