ATHENA/PRESTO complex query with multiple unnested tables - presto

Question

i have i would like to create a join over several tables.
table login : I would like to retrieve all the data from login
table logging : calculating the Nb_of_sessions for each db & for each a specific event type by user
table meeting : calculating the Nb_of_meetings for each db & for each user
table live : calculating the Nb_of_live for each db & for each user
I have those queries with the right results :
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;
But when i begin to try put it all together, it seems i retrieve bad data (i have only on db retrieved) and it seems not efficient.
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
Do you have an idea ?
Regards.

Answer 1

The easiest way is to work with with to structure the subquery and then reference them.
with parameter reference:
You can use WITH to flatten nested queries, or to simplify subqueries.
The WITH clause precedes the SELECT list in a query and defines one or
more subqueries for use within the SELECT query.
Each subquery defines a temporary table, similar to a view definition,
which you can reference in the FROM clause. The tables are used only
when the query runs.
Since you already have working sub queries, the following should work:
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;