I have the next row and what I want to do is to select all the rows before the type “shop”. I tried using case in the “where clause” but I didn’t get any result. How can I do it?
x
|id|visitnumber|type |
|01| 1|register|
|01| 2|visit |
|01| 3|visit |
|01| 4|shop |
|01| 5|visit |
For example, what I want to get is the visitnumber before type = “shop”.
it would be very helpful because what I’m trying to do is to get all the actions that happened before an specific event on big query.
|id|numberofvisits|
|01| 3|
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Answer
One method uses correlated subqueries:
select id, count(*)
from t
where visitnumber < (select min(t2.visitnumber) from t t2 where t2.id = t.id and type = 'shop')
group by id;
However, in BigQuery, I prefer an approach using window functions:
select id, countif(visitnumber < visitnumber_shop)
from (select t.*,
min(case when type = 'shop' then visitnumber end) over (partition by id) as visitnumber_shop
from t
) t
group by id;
This has the advantage of keeping all id
s even those that don’t have a “shop” type.