Database 按年份和月份计数记录，包括零计数

我使用的是SQL Server Compact Edition服务器，我想计算在一定日期范围内每月与某个教程相对应的评论数，包括计数为零的月份。我知道我需要将一个“日历”表加入到我的表中，以说明缺少的月份，但我需要帮助正确实现这一点

我有一个表格，里面有来自不同教程的所有评论。此表称为注释，我需要的列是

[Tutorial]

（

nvarchar

）和

[DateAdded]

（

DateTime

）

我有一个

日历

表，它有一个年和月列，如下所示：

Year | Month
-----+------
2000 | 01
2000 | 02
.    | .
.    | .
.    | .
2099 | 12

如果我在寻找过去一年（截至2014年2月14日）的每月“样本”评论数，那么理想的输出是：

Tutorial | Year | Month | Count
---------+------+-------+------
 sample  | 2013 |  09   |  7
 sample  | 2013 |  10   |  1
 sample  | 2013 |  11   |  6
 sample  | 2013 |  12   |  0
 sample  | 2014 |  01   |  0
 sample  | 2014 |  02   |  2

我能够找出如何执行以下查询，但我需要在没有注释的月份也返回0

SELECT 
     Tutorial, 
     datepart(year, DateAdded) AS Year, 
     datepart(month, DateAdded) AS Month, 
     COUNT(*) AS Count From Comments 
WHERE 
     DateAdded > DATEADD(year,-1,GETDATE())  
       AND 
     Tutorial='sample' 
GROUP BY 
     Tutorial, 
     datepart(year, DateAdded), 
     datepart(month, DateAdded)

使用上面的示例数据输出

Tutorial | Year | Month | Count
---------+------+-------+------
 sample  | 2013 |  09   |  7
 sample  | 2013 |  10   |  1
 sample  | 2013 |  11   |  6
 sample  | 2014 |  02   |  2

我知道我需要连接表，但我似乎无法确定要使用哪个连接或如何正确实现它。请记住，这是针对SQL Server CE的，因此并非所有来自SQL Server的命令都可以使用

---

非常感谢

下面是一个独立的脚本，您可以使用它进行尝试，而不必在生产环境中接触任何真实的数据库对象。代码的下三分之一包含您正在寻找的连接的帮助

SQLServerCE将允许您编写存储过程，而存储过程又可以用作报表的源。存储的进程很好，因为它们可以接受输入参数，这是执行报告的理想选择

-- create dummy Comments table for prototyping
create table #Comments (
    ID int identity(1,1) not null,
    Tutorial nvarchar(50) not null,
    DateAdded datetime not null,
    primary key clustered(DateAdded,ID,Tutorial)
);

-- populate dummy Comments table
declare @startDate datetime = '2000-01-01';
declare @endDate datetime = '2014-02-14';
declare @numTxns int = 5000;

set nocount on;

declare @numDays int = cast(@endDate as int) - cast(@startDate as int) + 1;
declare @i int = 1;
declare @j int = @i + @numTxns;
declare @rnd float;
while @i <= @j
begin
    set @rnd = RAND();
    insert into #Comments (Tutorial,DateAdded)
    select 
    -- random tutorial titles
        coalesce (
            case when @rnd < .25 then 'foo' else null end,
            case when @rnd between .5 and .75 then 'baz' else null end, 
            case when @rnd > .75 then 'qux' else null end,
            'bar'
        ) as Tutorial,
    -- random dates between @startDate and @endDate
        cast(cast(rand() * @numDays + @startDate as int) as datetime) as DateAdded
    set @i = @i + 1
end;

-- try deleting some months to see what happens
delete from #Comments
where DateAdded between '2013-11-01' and '2013-11-30'
    or DateAdded between '2014-01-01' and '2014-01-31';

set nocount off;
go

-- ### following could easily be rewritten as a stored procedure

-- stored procedure parameters
declare @startDate datetime = '2000-01-01';
declare @endDate datetime = '2014-03-31';
-- pick only one option below
--declare @Tutorial nvarchar(50) = 'foo'; -- this only gets data for Tutorials called 'foo'
declare @Tutorial nvarchar(50) = 'all'; -- this gets data for all tutorials

-- begin stored procedure code
set nocount on;

-- this temp table is an alternative to 
-- creating ***and maintaining*** a table full of dates,
-- months, etc., and cluttering up your database
-- in production, it will automatically delete itself
-- once the user has completed running the report.
create table #dates (
    DateAdded datetime not null,
    YearAdded int null,
    MonthAdded int null,
    primary key clustered (DateAdded)
);

-- now we put dates into #dates table
-- based on the parameters supplied by 
-- the user running the report
declare @date datetime = @startDate;
while @date <= @endDate
begin
    insert into #dates
    select @date, YEAR(@date), MONTH(@date);

    set @date = @date + 1;
end;

-- ## Why put every day of the month in this table?
-- ## I asked for a monthy report, not daily!
-- Yes, but looping through dates is easier, simply add 1 for the next date.
-- You can always build a monthly summary table later if you'd like.
-- This *is* kind of a brute-force solution, but easy to write.
-- More answers to this question in the code below, where they'll make more sense.

set nocount off;

-- now we return the data to the user
-- any month with no Tutorials will still show up in the report
-- but the counts will show as zero
select YearAdded, MonthAdded, SUM(Count_From_Comments) as Count_From_Comments,
    SUM(foo) as Count_Foo, SUM(bar) as Count_Bar, 
    SUM(baz) as Count_Baz, SUM(qux) as Count_Qux
from (
-- ## you can reuse the following code for a detail report by day
-- ## another answer to 'Why not by month?' from above
-- start daily report code
    select t1.DateAdded, t1.YearAdded, t1.MonthAdded, t2.Tutorial, 
            coalesce(Count_From_Comments,0) as Count_From_Comments, 
            case when t2.Tutorial = 'foo' then 1 else 0 end as foo,
            case when t2.Tutorial = 'bar' then 1 else 0 end as bar,
            case when t2.Tutorial = 'baz' then 1 else 0 end as baz,
            case when t2.Tutorial = 'qux' then 1 else 0 end as qux
    from #dates as t1 -- no where clause needed because #dates only contains the ones we want
    left join ( -- left join here so that we get all dates, not just ones in #Comments
        select *, 1 AS Count_From_Comments
        from #Comments
        where @Tutorial in (Tutorial,'all')
    ) as t2
        on t1.DateAdded = t2.DateAdded -- ## join on one field instead of two, another answer to 'Why not by month?' from above
-- end daily report code
) as qDetail
group by YearAdded, MonthAdded
order by YearAdded, MonthAdded

-- end stored procedure code
go

-- ## Not required in production code,
-- ## but handy when testing this script.
drop table #dates;

-- #### Since this will be a real table in production
-- #### we definitely only want this for testing!
drop table #Comments;

go

——为原型创建虚拟注释表
创建表#注释(
ID int标识（1,1）不为空，
教程nvarchar（50）不为空，
DateAdded datetime不为空，
主键群集（已添加日期、ID、教程）
);
--填充虚拟注释表
声明@startDate datetime='2000-01-01'；
声明@endDate datetime='2014-02-14'；
声明@numTxns int=5000；
不计数；
声明@numDays int=cast（@endDate为int）-cast（@startDate为int）+1；
声明@i int=1；
声明@j int=@i+@numTxns；
宣布@rnd浮动；
而@i.75然后'qux'则为空端，
“酒吧”
)作为教程，
--@startDate和@endDate之间的随机日期
强制转换（强制转换（rand（）*@numDays+@startDate为int）为datetime）为DateAdded
设置@i=@i+1
结束；
--尝试删除几个月，看看会发生什么
从#注释中删除
其中日期添加在“2013-11-01”和“2013-11-30”之间
或在“2014-01-01”和“2014-01-31”之间添加的日期；
不计数；
去
--######以下内容可以很容易地重写为存储过程
--存储过程参数
声明@startDate datetime='2000-01-01'；
声明@endDate datetime='2014-03-31'；
--只选择下面的一个选项
--声明@Tutorial nvarchar（50）=“foo”；--这只获取名为“foo”的教程的数据
声明@Tutorial nvarchar（50）=“全部”；--这将获取所有教程的数据
--开始存储过程代码
不计数；
--此临时表是一个替代表
--创建***并维护***一个充满日期的表格，
--几个月等等，把你的数据库弄得乱七八糟
--在生产中，它将自动删除自身
--一旦用户完成报告的运行。
创建表#日期(
DateAdded datetime不为空，
YearAdded int null，
蒙塔德整数为空，
主键群集（已添加日期）
);
--现在我们将日期放入#dates表中
--根据制造商提供的参数
--运行报表的用户
声明@date datetime=@startDate；
而@date如果你有一个
日历
表格，上面有
月
和
年
，你应该尝试以下方法

SELECT t2.Tutorial, t1.[Month], t1.[Year], COALESCE(t2.Number, 0) AS Result
  FROM Calendar AS t1 LEFT JOIN (
    SELECT 
      Tutorial, 
      CONVERT(NCHAR(6), DateAdded, 112) AS tutDate,
      COUNT(*) AS Count From Comments 
    WHERE 
      DateAdded > DATEADD(year,-1,GETDATE())  
      AND 
      Tutorial='sample' 
    GROUP BY 
      Tutorial, 
      CONVERT(NCHAR(6), [Order Date], 112)
  ) AS t2
  ON (t1.[Year] + t1.[Month]) = t2.tutDate
  ORDER BY t1.[Year] + t1.[Month]

这些都不适用于SQL CE
SELECT t2.Tutorial, t1.[Month], t1.[Year], COALESCE(t2.Number, 0) AS Result
  FROM Calendar AS t1 LEFT JOIN (
    SELECT 
      Tutorial, 
      CONVERT(NCHAR(6), DateAdded, 112) AS tutDate,
      COUNT(*) AS Count From Comments 
    WHERE 
      DateAdded > DATEADD(year,-1,GETDATE())  
      AND 
      Tutorial='sample' 
    GROUP BY 
      Tutorial, 
      CONVERT(NCHAR(6), [Order Date], 112)
  ) AS t2
  ON (t1.[Year] + t1.[Month]) = t2.tutDate
  ORDER BY t1.[Year] + t1.[Month]