How to Get First Row Per Group in Snowflake

Snowflake - Get First Row Per Group

If we have tables that include the data about sessions and users and want to view first session of all the users for a specific day, we can use the “row_number()” function. Example for “row_number()” function:

select
us.user_id1,
us.session_id1,
s.start_date1,
s.end_date1,
row_number() over (partition by user_id order by start_date1 desc) as row_number
from user_sessions1 us
left outer join sessions1 s on s.id1 = us.session_id1
Where to_varchar(start_date1, ‘dd-mm-yyyy’) = ‘06-02-2022’

This provides every Session ID of the day and its row number. As we only require the second session of the day, we only require a row that has row_number: 2. To get that, we have to utilise the common table expressions

with cte_sessions1 as (
select
us.user_id1,
us.session_id1,
s.start_date1,
s.end_date1,
row_number() over(partition by user_id1 order by start_date1 desc) as row_number
from user_sessions1 us
left outer join sessions1 s on s.id1 = us.session_id
where to_varchar(start_date1, ‘dd-mm-yyyy’) = ‘09-01-2022’
)
select *
from cte_sessions1
where row_number = 2;

Conclusion

The “row_number()” function is helpful for getting the required data, users, and sessions. I hope this provides you with the essential information about the “row_number()” function.

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