計算周

Question

數我所說的表日曆和數據的模樣：

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 

我要計算在MONTH_YEAR週數：

我寫了類似的查詢：

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 

這是給我我想要什麼，但有沒有更好的方法呢？

Answer 1

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

這可以刪除一個級別的聚合並且更具可讀性。不過，我不確定它是否會有更好的表現。

樣品概念證明：

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，這是你所需要的：

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