Question

I have three tables:

Table 1 – Members

Id   Name
1    Member1
2    Member2

Table 2 – Activity

Id   Member_id   Activity    Date
 1      1        Activity1   2001-1-1
 2      1        Activity2   2001-2-1
 3      1        Activity3   2001-3-1
 4      2        Test        2010-4-1

Table 3 – Detailed

Id  Activity_id Information
1   2       Information

From the following, the Member id 1 has three activities:

SELECT Member.id, COUNT(*) AS number
FROM Member 
INNER JOIN Activity ON Activity.Member_ID = Member.id
GROUP BY Member.id

My question is how I can find the id and date of the second activity (table 2) for all Members from table(1) who has 2 activities and also retrieve the information related to this activity id from table 3.

Thanks in advance

Answer 1

Row number function would help you here.

select *
from (
    select 
        *,
        rn = row_number() over (partition by member_id order by id)
    from
        activity
) activityWithRn
inner join detailed on detailed.activity_id = activityWithRn.id
where activityWithRn.rn = 2

Here I’ve partitioned the data by member id and the ordered the activity by its id but maybe you want to order by date?