Question

我有几个用于记录应用程序用户活动的表。这些表看起来像这样（来自内存的伪代码，可能在语法上不正确）：

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以用于报告目的，如下所示：

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

首先和最后的活动描述将按时间顺序确定。我最初的想法是像这样更新摘要表：

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，这对我来说似乎非常冗长和不必要。我只是不确定如何缩小它。我的直觉是我可以在insert语句中以某种方式完成它，但我很难过。有什么建议？

Answer 1

也许有更有效的方法可以做到这一点，但这最接近原作：

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;

这样的事情可能更有效：

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

粗略地说，

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)

Answer 4

或者，

INSERT等。

（SELECT description FROM detail d1 WHERE d1.sessionid = a.sessionid
AND NOT EXISTS（从创建的详细信息中选择1＆lt; d1.created））AS desc1，

（SELECT description FROM detail d2 WHERE d2.sessionid = a.sessionid
AND NOT EXISTS（选择1来自细节d2 WHERE创建＆gt; d1.created））AS desc2

FROM activity a

（我自己更喜欢这个。）

SQL Server - 使用另一个表中的第一行和最后一行更新一个表

4 个答案: