sql：根据月份计算总生日飞蛾

Question

我想编码查询来计算基于月份的总生日飞蛾。这里是示例数据。两人的星期二是1980年4月。

如何撰写此查询？

John 02/21/1980 
Peter 02/22/1980 
Lucy 04/21/1980 

------ result ----- 
01/1980  0 
02/1980  2 
03/1980  0 
04/1980  1 
05/1980  0 
..... 

Answer 1

这个怎么样的SQL服务器

create table #temp 
(
    name varchar(50), 
    DOB datetime 
) 

insert into #temp values ('john', '2/21/1980') 
insert into #temp values ('peter', '2/22/1980') 
insert into #temp values ('lucy', '4/21/1980') 

select convert(varchar(2), MONTH(DOB)) + '/' + Convert(varchar(4), YEAR(DOB)) as [MM/YYYY] 
    , count(*) as TotalCount 
from #temp 
group by convert(varchar(2), MONTH(DOB)) + '/' + Convert(varchar(4), YEAR(DOB)) 

drop table #temp 

编辑 - 这将让你的日期中的所有记录包含在表的日期。它将使用最小/最大日在表中获取日期范围内，然后使用这个范围内得到生日每个月计数：

create table #temp 
(
    name varchar(50), 
    DOB datetime 
) 

insert into #temp values ('john', '2/21/1980') 
insert into #temp values ('peter', '2/22/1980') 
insert into #temp values ('lucy', '4/21/1980') 

;with cte as 
(
    select min(DOB) as MinDate, max(DOB) as MaxDate 
    from #temp 
    union all 
    SELECT dateadd(mm, 1, t.MinDate), t.MaxDate 
    from cte t 
    where dateadd(mm, 1, t.MinDate) <= t.MaxDate 
) 
select convert(varchar(2), MONTH(c.MinDate)) + '/' + Convert(varchar(4), YEAR(c.MinDate)) 
    , IsNull(t.TotalCount, 0) as TotalCount 
from cte c 
LEFT JOIN 
(
    SELECT convert(varchar(2), MONTH(DOB)) + '/' + Convert(varchar(4), YEAR(DOB)) as [MM/YYYY] 
     , count(*) as TotalCount 
    FROM #temp 
    group by convert(varchar(2), MONTH(DOB)) + '/' + Convert(varchar(4), YEAR(DOB)) 
) t 
    on convert(varchar(2), MONTH(C.MinDate)) + '/' + Convert(varchar(4), YEAR(C.MinDate)) 
     = t.[MM/YYYY] 

drop table #temp 

Answer 2

在MySQL中你可以这样做：

select concat(month(dob), '/', year(dob)) monthYear, count(*) cnt from t 
group by monthYear 
order by year(dob), month(dob) 

但是，为了获得“缺失日期”，您必须生成数据，因为01/1980不在任何表格中，据我所知。检查这个answer看看如何。

Answer 3

您可以循环像这样每个月：

DECLARE @month INT 
DECLARE @year INT 
DECLARE @result TABLE (MonthYear varchar(7),BirthdaysCount INT) 
SET @month = 1 
SET @year = 1980 

WHILE(@month < 13) 
    BEGIN 
    INSERT INTO @result 
    SELECT (CAST(@month as VARCHAR) + '/' + CAST(@year as VARCHAR)), 
      COUNT(*) 
    FROM test 
    WHERE MONTH(birth) = @month AND YEAR(birth) = @year 
    SET @month = @month + 1 
    END 

select * from @result 

见琴：http://sqlfiddle.com/#!3/20692/2