具有多个未嵌套表的 ATHENA/PRESTO 复杂查询

Question

我想在多个表上创建一个联接。 表登录：我想从登录中检索所有数据 表记录：按用户计算每个数据库和每个特定事件类型的 Nb_of_sessions 表会议：计算每个数据库和每个用户的 Nb_of_meetings 实时表：计算每个数据库和每个用户的 Nb_of_live

我有正确的结果：

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,userid;

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;

但是当我开始尝试将它们放在一起时，似乎我检索到了错误的数据（我只检索了 db 上的数据）并且似乎效率不高。

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

你有什么想法吗？

问候。

Answer 1

最简单的方法是使用with 构造子查询，然后引用它们。

with parameter参考：

您可以使用 WITH 来展平嵌套查询，或简化子查询。

WITH 子句在查询中位于 SELECT 列表之前，并定义一个或 在 SELECT 查询中使用更多子查询。

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

由于您已经有工作子查询，以下应该可以工作：

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,userid
)
,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;