sql - 使用递归公用表表达式(如 while 循环)

Question

我有下表

   Log

 Date            date
 Description     varchar
 ID              integer

给定一个日期作为参数，我必须找到编号。或从开始日期到其后一个月使用递归 cte 每天记录的日志计数。 有些天可能没有任何日志，所以我必须将计数打印为 0。

例如:

  select * from Log

返回

  1   insert      2011-01-17
  2   blah blah   2011-01-23
  3   blah        2011-07-07

对于 2011-01-17 作为输入，输出应该是

   2011-01-17    1
   2011-01-18    0
   2011-01-19    0
   ....
   2011-01-23    1
   .....
   2011-02-17    0

我必须使用递归cte来做到这一点。我不知道如何在每次递归中将日期加1以及如何停止\终止递归。

这是我迄今为止所做的事情:

 with cte as    (
    select '2011-01-17' as dat,count(*) as count 
from log group by date 
having date='2011-01-17' 

union all 

select dateadd(day,1,dat) as dat,count(*) as count 
from log,cte 
group by date 
having date=dateadd(day,1,dat) 
where dat<'2011-02-17' 
) 
select * from cte

Answer 1

WITH    days (d, maxd) AS
        (
        SELECT  MIN(date), MAX(date)
        FROM    log
        UNION ALL
        SELECT  DATEADD(day, 1, d), maxd
        FROM    days
        WHERE   d < maxd
        )
SELECT  d, COUNT(id)
FROM    days
LEFT JOIN
        log l
ON      l.date = d
GROUP BY
        d