SQL服务器 - 更新一个表与另一个表的第一行和最后一行

Question

我有一对夫妇被用来记录用户活动的申请表。该表看起来是这样的（从内存伪代码，可能不是语法正确）：

create table activity (
  sessionid uniqueidentifier not null,
  created smalldatetime not null default getutcdate()
);

create table activity_details (
  sessionid uniqueidentifier not null,
  activity_description varchar(100) not null,
  created smalldatetime not null default getutcdate()
);

我的目标是填充汇总表报告的目的，看起来是这样的：

create table activity_summary (
  sessionid uniqueidentifier not null,
  first_activity_desc varchar(100) not null,
  last_activity_desc varchar(100) not null
);

第一个和最后的活动说明会按时间顺序确定。我最初的想法是更新汇总表如下所示：

truncate table activity_summary;

insert into activity_summary (sessionid)
select sessionid from activity;

update table activity_summary set
  first_activity_desc = (select top 1 activity_desc from activity_detail where sessionid = as.sessionid order by created asc),
  last_activity_summary = (select top 1 activity_desc from activity_detail where sessionid = as.sessionid order by created desc)
from activity_summary as;

然而，这似乎令人难以置信的冗长和不必要的给我。我只是不知道如何缩小下来。我的直觉是，我可以将所有的INSERT语句中做到这一点不知怎么的，但我很为难。有什么建议么？

Answer 1

有可能是更有效的方式来做到这一点为好，但这是最接近原始的：

truncate table activity_summary;

insert into activity_summary (sessionid, first_activity_desc, last_activity_summary)
select a.sessionid
,(select top 1 ad.activity_desc from activity_detail AS ad where ad.sessionid = a.sessionid order by ad.created asc) AS first_activity_desc
,(select top 1 ad.activity_desc from activity_detail AS ad where ad.sessionid = a.sessionid order by ad.created desc) AS last_activity_summary
from activity AS a;

像这样的东西可能更有效：

truncate table activity_summary;

WITH firsts AS (
    SELECT ad.sessionid
        ,ad.activity_desc
        ,ROW_NUMBER() OVER (ORDER BY ad.created ASC) as RowNumber
    FROM activity_detail AS ad
)
,lasts AS (
    SELECT ad.sessionid
        ,ad.activity_desc
        ,ROW_NUMBER() OVER (ORDER BY ad.created DESC) as RowNumber
    FROM activity_detail AS ad
)
insert into activity_summary (sessionid, first_activity_desc, last_activity_summary)
select a.sessionid
    ,firsts.activity_desc
    ,lasts.activity_desc
from activity AS a
INNER JOIN firsts ON firsts.sessionid = a.sessionid AND firsts.RowNumber = 1
INNER JOIN lasts ON lasts.sessionid = a.sessionid AND lasts.RowNumber = 1

Answer 2

insert into activity_summary
    (sessionid, first_activity_desc, last_activity_desc)
select
    agg.sessionid,
    adf.activity_description,
    adl.activity_description
from
    (SELECT
         sessionid, MIN(created) as firstcreated, MAX(created) as lastcreated
    from
         activity_detail group by sessionid
    ) agg
    JOIN
    activity_details adf ON agg.sessionid = adf.sessionid AND agg.firstcreated = adf.created
    JOIN
    activity_details adl ON agg.sessionid = adl.sessionid AND agg.lastcreated = adl.created

Answer 3

要么，

INSERT等。

（SELECT描述FROM细节D1 WHERE d1.sessionid = a.sessionid AND NOT EXISTS（SELECT 1 FROM细节WHERE创建<d1.created））AS DESC1，

（SELECT描述FROM细节D2 WHERE d2.sessionid = a.sessionid AND NOT EXISTS（SELECT 1 FROM WHERE创建> d1.created细节D2）AS DESC2）

FROM活动

（我喜欢这一个自己。）

Answer 4

大致，

INSERT等。

SELECT a.sessionid, d1.activity_description, d2.activity_description

FROM activity a

JOIN detail d1 ON a.sessionid = d1.sessionid
JOIN detail d2 ON a.sessionid = d2.sessionid

WHERE NOT EXISTS  
  (SELECT 1 FROM detail WHERE sessionid = a.sessionid AND created < d1.created)

AND NOT EXISTS  
  (SELECT 1 FROM detail WHERE sessionid = a.sessionid AND created > d2.created)