具有多个未嵌套表的ATHENA / PRESTO复杂查询

问题描述

我想在多个表上创建联接。表登录：我想从登录中检索所有数据表记录：按用户为每个数据库和每个特定事件类型计算Nb_of_sessions 表会议：为每个数据库和每个用户计算Nb_of_meetings table live：为每个数据库和每个用户计算Nb_of_live

我的查询结果正确：

SELECT db.id,_id as userid,firstname,lastname
FROM  "logins"."login",UNnesT(dbs) AS a1 (db)

SELECT dbid,userid,count(distinct(sessionid)) as no_of_visits,array_join(array_agg(value.from_url),',') as from_url
FROM "loggings"."logging"
where event='url_event'
group by db.id,userid;

SELECT dbid,userid AS userid,count(*) as nb_interviews,array_join(array_agg(interviewer),') as interviewer 
FROM  "meetings"."meeting" 
group by dbid,r1.user._id AS userid,count(_id) as nb_chat 
FROM "lives"."live",UNnesT(users) AS r1 (user)
group by dbid,r1.user._id;

但是当我开始尝试将它们放在一起时，似乎我检索了不良数据（我只检索了数据库），而且效率似乎不高。

select a1.db.id,a._id as userid,a.firstname,a.lastname,count(rl._id) as nb_chat
FROM 
"logins"."login" a,"loggings"."logging" b,"meetings"."meeting" c,"lives"."live" d,UNnesT(dbs) AS a1 (db),UNnesT(users) AS r1 (user)
where a._id = b.userid AND a._id = c.userid AND a._id = r1.user._id
group by 1,2,3,4

你有个主意吗？

致谢。

解决方法

最简单的方法是使用with来构造子查询，然后对其进行引用。

with parameter参考：

您可以使用WITH来平整嵌套查询或简化子查询。

WITH子句在查询中的SELECT列表之前，并定义一个或更多子查询供SELECT查询中使用。

每个子查询定义一个临时表，类似于视图定义，您可以在FROM子句中引用。这些表仅用于查询运行时。

由于您已经具有有效的子查询，因此以下各项应该起作用：

with logins as 
(
    SELECT db.id,_id as userid,firstname,lastname
    FROM  "logins"."login",UNNEST(dbs) AS a1 (db)
),visits as
(
    SELECT dbid,userid,count(distinct(sessionid)) as no_of_visits,array_join(array_agg(value.from_url),',') as from_url
    FROM "loggings"."logging"
    where event='url_event'
    group by db.id,userid
),meetings as
(
    SELECT dbid,userid AS userid,count(*) as nb_interviews,array_join(array_agg(interviewer),') as interviewer 
    FROM  "meetings"."meeting" 
    group by dbid,chats as 
(
    SELECT dbid,r1.user._id AS userid,count(_id) as nb_chat 
    FROM "lives"."live",UNNEST(users) AS r1 (user)
    group by dbid,r1.user._id
)
select *
from logins l
left join visits v
    on l.dbid = v.dbid
    and l.userid = v.userid
left join meetings m
    on l.dbid = m.dbid
    and l.userid = m.userid
left join chats c
    on l.dbid = c.dbid
    and l.userid = c.userid;

amazon-athena presto unnest