Hello, I want to perform join using not a primary key. Is it possible?
What I need is something like the SQL below:
select *
from activity
left join activity as future_activity on
activity.user_id = future_activity.user_id
and activity.date = future_activity.date - interval ‘1 day’
I understand syntax does not support it. But maybe you guys know a workaround? (I tried to perform a join of select, but obviously failed).
Thank you very much in advance!
Hi @Viacheslav
You should try to have parent-child relationship via child referencing the parent’s document-id.
Logically, this will be the equivalent query:
select *
from activity
left join activity as future_activity ON KEYS
activity.user_id = meta(future_activity).id /* future_activity.user_id */
WHERE date_diff_str(activity.date, future_activity.date, “day”) = 1;
actual query is:
select *
from activity
left join activity as future_activity ON KEYS
activity.user_id
WHERE date_diff_str(activity.date, future_activity.date, “day”) = 1;
If the document id is a composite key, you can concatnate the values to form a ON KEYS expression.
With Couchbase, you can join from parent-to-child as well.
See this article https://dzone.com/articles/join-faster-with-couchbase-index-joins for details.
@keshav_m Hello Kechav, thank you for the fast answer.
I’m not sure I follow your idea.
You wrote:
activity.user_id = meta(future_activity).id /* future_activity.user_id */
You commented out future_activity.user_id: but this is what I actually need: activity.user_id = future_activity.user_id as activity.user_id definitely can not be a primary key in future_activity because it’s the same “table”.
Here http://developer.couchbase.com/documentation/server/current/n1ql/n1ql-language-reference/from.html all forms of joins / nest / unnest requires a primary key for LHS or RHS. Though it’s said:
ON [ PRIMARY ] KEY rhs-expression.lhs-expression-key FOR lhs-expression
I like the word expression in lhs-expression. This is an expression! A subquery?? But again use keys is mandatory for subqueries.
As I understand you offer somehow to turn it to a situation with “parent-child”, and I don’t mind to modify my data to make it possible. But I don’t see how. Maybe you know a trick or a common practice having such an impressive experience?
Thank you very much for your attention indeed!
The query you mentioned is the LOGICAL equivalent. Below is the ACTUAL query syntax.
select *
from activity
left join activity as future_activity
ON KEYS activity.user_id
WHERE date_diff_str(activity.date, future_activity.date, "day") = 1;activity.user_id is not a primary key in future_activity, so it can not work, unfortunately
Do you suppose to support join not by primary-keys in the future?
What we are trying to achieve is finding out if a user is a new subscriber to our services during a calendar month. We would know if they are a new subscriber if they did not make a subscription last month (note: some subscribers are resurrected so querying the first time they made a subscription payment ever does not work).
The subscription payment document has the following schema:
{
“doc_type”:“subspayment”,
“account_uid”:“acc_HAYPTvMCDGCShwmBFeJqSc”,
“created”:“2015-10-10T12:30:40”
}
The created property is the date when a subscription payment was made. If the account made a payment in October we want to know if they also made a payment in September. If they did not then they are a new user. We would like to be able to get a data series (daily / weekly / monthly) data series of new users.
This type of query is extremely useful for SAAS companies who need to calculate retention metrics etc. for reporting purposes.
Thanks very much for taking a look!
Hi @cwoolgar
I tried this, trying to mimic the model you gave. See the query below.
If you give full sample documents with document-keys, we can try that.
In Couchbase (and NoSQL in general), document key design is important since they form the reference/relationship.
select meta().id as dockey, * from pay;
[
{
"dockey": "subpayment::ca0bef29-0007-4d1b-a8cc-6671151a6b36",
"pay": {
"account_uid": "user::acc_HAYPTvMCDGCShwmBFeJqSc",
"created": "2015-08-21T12:30:40",
"doc_type": "subspayment"
}
},
{
"dockey": "subpayment::cc9d320b-6eb0-48f2-a59b-b187739318f2",
"pay": {
"account_uid": "user::acc_HAYPTvMCDGCShwmBFeJqSc",
"created": "2015-04-21T12:30:40",
"doc_type": "subspayment"
}
},
{
"dockey": "subpayment::f52cfa5f-1ca1-4c04-a475-dead49988d97",
"pay": {
"account_uid": "user::acc_HAYPTvMCDGCShwmBFeJqSc",
"created": "2015-03-23T12:30:40",
"doc_type": "subspayment"
}
},
{
"dockey": "subpayment::fbb6c992-e189-4edd-97ce-c64a8ef16faa",
"pay": {
"account_uid": "user::acc_HAYPTvMCDGCShwmBFeJqSc",
"created": "2015-05-21T12:30:40",
"doc_type": "subspayment"
}
},
{
"dockey": "user::acc_HAYPTvMCDGCShwmBFeJqSc",
"pay": {
"fname": "John",
"lname": "Miller",
"udate": "2015-10-10T12:30:40",
"zip": 94523
}
}
]
select *
FROM pay p USE KEYS ["user::acc_HAYPTvMCDGCShwmBFeJqSc"]
INNER JOIN pay s ON KEY s.account_uid FOR p
WHERE date_diff_str(p.udate, s.created, "month") = 1;Hello - thanks for your reply.
Here is a sample of data for each subscription document. There are 3 accounts and what we need to know is when they started subscribing by looking at whether they made a payment the month before also. If they did not make a payment the month before then they are considered newly subscribed.
{
“account_uid”:“acc_HAYPTvMCDGCShwmBFeJqSc”,
“created”:“2015-09-09T12:30:40”
}
{
“account_uid”:“acc_HAYPTvMCDGCShwmBFeJqSc”,
“created”:“2015-10-10T12:30:40”
}
{
“account_uid”:“acc_HTEQTvMCDGCShwmBFeJqSc”,
“created”:“2015-10-10T12:30:40”
}
{
“account_uid”:“acc_HTEQTvMCDGCShwmBFeJqSc”,
“created”:“2015-11-05T12:30:40”
}
{
“account_uid”:“acc_UTCQTvMCDGCShwmBFeJqSc”,
“created”:“2015-10-10T12:30:40”
}
{
“account_uid”:“acc_UTCQTvMCDGCShwmBFeJqSc”,
“created”:“2015-11-05T12:30:40”
}
and the output from the query:
date_series new_accounts
2015-09 1
2015-10 2
Thanks
Catherine
SELECT * FROM c;
[
{
"c": {
"account_uid": "acc_UTCQTvMCDGCShwmBFeJqSc",
"created": "2015-11-05T12:30:40"
}
},
{
"c": {
"account_uid": "acc_HAYPTvMCDGCShwmBFeJqSc",
"created": "2015-10-10T12:30:40"
}
},
{
"c": {
"account_uid": "acc_HAYPTvMCDGCShwmBFeJqSc",
"created": "2015-09-09T12:30:40"
}
},
{
"c": {
"account_uid": "acc_HTEQTvMCDGCShwmBFeJqSc",
"created": "2015-10-10T12:30:40"
}
},
{
"c": {
"account_uid": "acc_HTEQTvMCDGCShwmBFeJqSc",
"created": "2015-11-05T12:30:40"
}
},
{
"c": {
"account_uid": "acc_UTCQTvMCDGCShwmBFeJqSc",
"created": "2015-10-10T12:30:40"
}
}
]
SELECT account_uid, max(created)
FROM c
GROUP BY account_uid
HAVING (DATE_DIFF_STR("2015-11-15T12:30:40", max(created), "month")) > 0
[
{
"$1": "2015-10-10T12:30:40",
"account_uid": "acc_HAYPTvMCDGCShwmBFeJqSc"
}
]
SELECT account_uid, max(created)
FROM c
GROUP BY account_uid
HAVING (DATE_DIFF_STR("2016-11-15T12:30:40", max(created), "month")) > 0;
[
{
"$1": "2015-10-10T12:30:40",
"account_uid": "acc_HAYPTvMCDGCShwmBFeJqSc"
},
{
"$1": "2015-11-05T12:30:40",
"account_uid": "acc_HTEQTvMCDGCShwmBFeJqSc"
},
{
"$1": "2015-11-05T12:30:40",
"account_uid": "acc_UTCQTvMCDGCShwmBFeJqSc"
}
]
SCROLL the window above to see additional queries.
Add the grouping of these results by month (use the date functions…)
SELECT (TOSTR(date_part_str(dcreated, "year")) || "-" || TOSTR(date_part_str(dcreated, "month"))) as month, count(1) total
FROM
(SELECT account_uid, max(created) as dcreated
FROM c
GROUP BY account_uid
HAVING (DATE_DIFF_STR("2016-11-15T12:30:40", max(created), "month")) > 0 ) AS newacts
GROUP BY (TOSTR(date_part_str(dcreated, "year")) || "-" || TOSTR(date_part_str(dcreated, "month")))
[
{
"month": "2015-11",
"total": 2
},
{
"month": "2015-10",
"total": 1
}
]