Question

I have a table like this:

id |    action       |  user_id
1       'test'          'person1'
2       'entered'       'person2'
3       'KEYPHRASE1'    'person1'
4       'entered'       'person1'

I need to do a select and return the user_id of the ‘entered’ action. However, I need to grab this ‘entered’ action only after the last occurence of either of these phrases: ‘KEYPHRASE1’, ‘KEYPHRASE2’,
‘KEYPHRASE3’, ‘KEYPHRASE4’, ‘KEYPHRASE5’, and ‘KEYPHRASE6’. If the ‘entered’ action does not occur after the last occurence of either of these KEYPHRASEs, then return null.

(So, in this example, the query should return ‘person1’ and not ‘person2’)

Answer 1

This seems like a correlated subquery in the where clause solution:

select user_id
from t
where t.action = 'entered' and
      exists (select 1
              from t t2
              where t2.id < t1.id and
                    t2.user_id = t1.user_id and
                    t2.action in ('KEYPHRASE1', 'KEYPHRASE2', 'KEYPHRASE3', 'KEYPHRASE4', 'KEYPHRASE5', 'KEYPHRASE6')

The above checks that the actions are after one of the last ones. Answering the question as written (after the last one) can be done with an aggregation:

select user_id
from t
group by user_id
having (max(case when t.action = 'Entered' then id end) >
        max(case when t2.action in ('KEYPHRASE1', 'KEYPHRASE2', 'KEYPHRASE3', 'KEYPHRASE4', 'KEYPHRASE5', 'KEYPHRASE6') then id
           end)
       )