计算SQL中列的每个唯一组合的行

Question

我想从一个表格中返回一个基于两列的唯一记录，以及最近的发布时间以及这两个列的组合在（及时）记录之前出现的总次数。输出。

所以我想要得到的是以下几方面的东西：

select col1, col2, max_posted, count from T
join (
 select col1, col2, max(posted) as posted  from T where groupid = "XXX" 
group by col1, col2) h
on ( T.col1 = h.col1 and
  T.col2 = h.col2 and
  T.max_posted = h.tposted)
where T.groupid = 'XXX'

计数需要为输出中每个记录的max_posted之前col1和col2的每种组合发生的次数。 （我希望我能正确解释：）

编辑：尝试以下建议：

 select dx.*,
   count(*) over (partition by dx.cicd9, dx.cdesc order by dx.tposted) as   cnt
from dx
join (
select cicd9, cdesc, max(tposted) as tposted  from dx where groupid ="XXX" 
group by cicd9, cdesc) h
on ( dx.cicd9 = h.cicd9 and
  dx.cdesc = h.cdesc and
  dx.tposted = h.tposted)
where groupid =  'XXX';

计数始终返回“ 1”。 此外，您将如何仅计算发过tposted之前发生的记录？

这也失败了，但是我希望你能达到我的目标：

  WITH H AS (
    SELECT cicd9, cdesc, max(tposted) as tposted  from dx where groupid =  'XXX' 
    group by cicd9, cdesc), 
    J AS (
    SELECT  count(*) as cnt
    FROM dx, h
    WHERE dx.cicd9 = h.cicd9
      and dx.cdesc = h.cdesc
      and dx.tposted <= h.tposted
      and dx.groupid = 'XXX'
 )
SELECT H.*,J.cnt
FROM H,J 

帮助任何人？

Answer 1

这个怎么样：

SELECT DISTINCT ON (cicd9, cdesc) cicd9, cdesc,
  max(posted) OVER w AS last_post,
  count(*) OVER w AS num_posts
FROM dx
WHERE groupid = 'XXX'
WINDOW w AS (
  PARTITION BY cicd9, cdesc
  RANGE BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING
);

鉴于缺少PG版本，表定义，数据和所需的输出，这只是从臀部拍摄而已，但是原理应该起作用：在两列上进行分区，其中groupid = 'XXX' ，然后找到已posted的最大值列和窗口框架中的总行数（因此，窗口定义中的RANGE...子句）。

Answer 2

您是否只想累积计数？

select t.*,
       count(*) over (partition by col1, col2 order by posted) as cnt
from table t
where groupid = 'xxx';

Answer 3

这是我能提出的最好的建议-欢迎提出更好的建议！

这将产生我需要的结果，但要理解，计数将始终至少为1（来自连接）：

  SELECT dx.cicd9, dx.cdesc, max(dx.tposted), count(*)
from dx 
join (
SELECT cicd9, cdesc, max(tposted) as tposted  from dx where groupid   =  'XXX' 
    group by cicd9, cdesc) h
on 
  (dx.cicd9 = h.cicd9 and dx.cdesc = h.cdesc and dx.tposted <= h.tposted 
  and dx.groupid = 'XXX')
group by dx.cicd9, dx.cdesc
order by dx.cdesc;

要么

 WITH H AS (
    SELECT cicd9, cdesc, max(tposted) as tposted  from dx where groupid =  'XXX' 
    group by cicd9, cdesc)  
SELECT dx.cicd9, dx.cdesc, max(dx.tposted), count(*)
from dx, H
where dx.cicd9 = h.cicd9 and dx.cdesc = h.cdesc and dx.tposted <= h.tposted 
  and dx.groupid = 'XXX'
group by dx.cicd9, dx.cdesc
order by cdesc;

Answer 4

这令人困惑：

计数需要为输出中每个记录的max_posted之前col1和col2的每种组合发生的次数。

根据定义，由于每条记录都在最新帖子的“之前”（或与最新帖子同时），因此，这实际上意味着每个组合的总计数 （忽略句子中假定的一个错误）。

因此，这可以归结为一个简单的GROUP BY ：

SELECT cicd9, cdesc
     , max(posted) AS last_posted
     , count(*)    AS ct
FROM   dx
WHERE  groupid = 'XXX'
GROUP  BY 1, 2
ORDER  BY 1, 2;

与目前接受的答案完全相同 。 只是更快，更简单。