如何按类别分隔 SQL 分区：“row_number() over (partition by...”？

Question

I am working with some app events data and looking to group the event sets of a specific action together, in order to grab the most recent event set. The customer (customer_id) starts the event set with 'step 1' (EventStep) and can go all the way through step 4 (or can drop out at any step along the way). The event set can be triggered by a few actions (EventTrigger).

Goal: Grab all the steps of the most recent event set, and identify the date (based on Timestamp) and EventTrigger.

Issue

There should only be 1 EventTrigger for each event set but the way my code is written, it combined event steps from different EventTriggers ( if the customer advanced further along in previous attempts than in most recent attempts). How do I ensure the event steps are grouped by the EventTrigger?

My code

SELECT * FROM (
    SELECT customer_id
         , EventStep
         , Timestamp
         , EventTrigger
         , ROW_NUMBER() OVER (PARTITION BY customer_id, EventStep ORDER BY Timestamp DESC) AS row_num
    FROM xxx_table
) xxx
WHERE row_num = 1

Actual Results

Image 1:

Wanted Results

Image 2

The ID field is something I created that labels the events in the order that they happened so that you can visualize what I'm looking for better.

Answer 1

I think you want:

SELECT xxx.*
FROM (SELECT xxx.*,
             ROW_NUMBER() OVER (PARTITION BY customer_id, EventStep ORDER BY Timestamp DESC) AS seqnum
      FROM xxx_table xxx
     ) xxx
WHERE seqnum = 1;

Nothing in your question suggests that aggregation is necessary.

EDIT:

Are you just looking for dense_rank() :

select xxx.*,
       dense_rank() over (partition by customer_id order by Timestamp) as seqnum
from xxx_table xxx;

Answer 2

To paraphrase, you want the most recent events for each customer, stopping at the most recent Step1?

SELECT
  xxx_table.*
FROM
  xxx_table
INNER JOIN
(
  SELECT customer_id, MIN(timestamp) AS timestamp
    FROM xxx_table
   WHERE EventStep = 'Step 1'
)
  AS cust_endpoint
     ON  cust_endpoint.customer_id  = xxx_table.customer_id
     AND cust_endpoint.timestamp   >= xxx_table.timestamp