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Question

I have a copy of our salesforce data in bigquery, I'm trying to join the contact table together with the account table.

I want to return every account in the dataset but I only want the contact that was created first for each account.

I've gone around and around in circles today googling and trying to cobble a query together but all roads either lead to no accounts, a single account or loads of contacts per account (ignoring the earliest requirement).

Here's the latest query. that produces no results. I think I'm nearly there but still struggling. any help would be most appreciated.

---

SELECT distinct  
 c.accountid as Acct_id 
,a.id as a_Acct_ID
,c.id as Cont_ID
,a.id AS a_CONT_ID 
,c.email
,c.createddate

FROM `sfdcaccounttable` a

INNER JOIN `sfdccontacttable` c
ON c.accountid = a.id

INNER JOIN
    (SELECT a2.id, c2.accountid, c2.createddate AS MINCREATEDDATE
    FROM `sfdccontacttable` c2

    INNER JOIN `sfdcaccounttable` a2 ON a2.id = c2.accountid

 GROUP BY 1,2,3
 ORDER BY c2.createddate asc LIMIT 1) c3 
ON c.id = c3.id

ORDER BY a.id asc

LIMIT 10

Answer 1

The solution shared above is very BigQuery specific: it does have some quirks you need to work around like the memory error you got.

I once answered a similar question here that is more portable and easier to maintain.

Essentially you need to create a smaller table(even better to make it a view) with the ID and it's first transaction. It's similar to what you shared by slightly different as you need to group ONLY in the topmost query.

It looks something like this

select 
# contact ids that are first time contacts
b.id as cont_id,
b.accountid

from `sfdccontacttable` as b inner join 
(   select accountid,
    min(createddate) as first_tx_time
    FROM `sfdccontacttable`  
    group by 1) as a on (a.accountid = b.accountid and b.createddate = a.first_tx_time)
group by 1, 2

You need to do it this way because otherwise you can end up with multiple IDs per account (if there are any other dimensions associated with it). This way also it is kinda future proof as you can have multiple dimensions added to the underlying tables without affecting the result and also you can use a where clause in the inner query to define a "valid" contact and so on. You can then save that as a view and simply reference it in any subquery or join operation

Answer 2

Setup a view/subquery for client_first or client_last

as:

SELECT * except(_rank) from (
  select rank() over (partition by accountid order by createddate  ASC) as _rank, 
   * 
   FROM `prj.dataset.sfdccontacttable`  
)  where _rank=1

basically it uses a Window function to number the rows, and return the first row, using ASC that's first client, using DESC that's last client entry.

You can do that same for accounts as well, then you can join two simple, as exactly 1 record will be for each entity.

UPDATE

You could also try using ARRAY_AGG which has less memory footprint.

#standardSQL
SELECT e.* FROM (
  SELECT ARRAY_AGG(
    t ORDER BY t.createddate ASC LIMIT 1
  )[OFFSET(0)]  e
  FROM `dataset.sfdccontacttable` t 
  GROUP BY t.accountid 
)