Recreate GA Funnel on BigQuery

Question

I am trying to recreate the GA funnel (custom report on Google360) using BigQuery. The funnel on GA is using the unique count of events that happen on each page. I found this query online that is working for the most part:

SELECT
  COUNT( s0.firstHit) AS Landing_Page,
  COUNT( s1.firstHit) AS Model_Selection
from(
SELECT
      s0.fullvisitorID,
      s0.firstHit,
      s1.firstHit,
    FROM (
            # Begin Subquery #1 aka s0
            SELECT
                    fullvisitorID,
                    MIN(hits.hitNumber) AS firstHit
            FROm [64269470.ga_sessions_20170720]
            WHERE
                  hits.eventInfo.eventAction  in ('landing_page') 
                    AND totals.visits = 1
            GROUP BY
                  fullvisitorID
                  ) s0
    # End Subquery #1 aka s0

    left join (

    # Begin Subquery #2 aka s1
          SELECT
              fullvisitorID,
              MIN(hits.hitNumber) AS firstHit
          FROM [64269470.ga_sessions_20170720]
          WHERE
            hits.eventInfo.eventAction  in ('model_selection_page')
            AND totals.visits = 1
          GROUP BY
                fullvisitorID,
                ) s1

      ON
    s0.fullvisitorID = s1.fullvisitorID

    )

The query works fine and the value for landing page is the same as I can get on GA, but Model_Selection is about 10% higher. This difference also increases along the funnel (I only posted 2 steps for clarity). Any idea what am I missing here?

Answer 1

This query does what you need but in Standard SQL Version:

#standardSQL
SELECT 
  SUM((SELECT COUNTIF(eventInfo.eventAction = 'landing_page') FROM UNNEST(hits))) Landing_Page,
  SUM((SELECT COUNTIF(eventInfo.eventAction = 'model_selection_page') FROM UNNEST(hits) WHERE EXISTS(SELECT 1 FROM UNNEST(hits) WHERE eventInfo.eventAction = 'landing_page'))) Model_Selection  
FROM `64269470.ga_sessions_20170720`

Just that. 4 lines, way faster and cheaper.

You can also play with simulated data, something like:

#standardSQL
WITH data AS(
  SELECT '1' AS fullvisitorid, ARRAY<STRUCT<eventInfo STRUCT<eventAction STRING > >> [STRUCT(STRUCT('landing_page' AS eventAction) AS eventInfo)] AS hits UNION ALL
  SELECT '1' AS fullvisitorid, ARRAY<STRUCT<eventInfo STRUCT<eventAction STRING > >> [STRUCT(STRUCT('landing_page' AS eventAction) AS eventInfo), STRUCT(STRUCT('landing_page' AS eventAction) AS eventInfo)] AS hits UNION ALL
  SELECT '1' AS fullvisitorid, ARRAY<STRUCT<eventInfo STRUCT<eventAction STRING > >> [STRUCT(STRUCT('landing_page' AS eventAction) AS eventInfo), STRUCT(STRUCT('model_selection_page' AS eventAction) AS eventInfo)] AS hits UNION ALL
  SELECT '1' AS fullvisitorid, ARRAY<STRUCT<eventInfo STRUCT<eventAction STRING > >> [STRUCT(STRUCT('model_selection_page' AS eventAction) AS eventInfo), STRUCT(STRUCT('model_selection_page' AS eventAction) AS eventInfo)] AS hits
)

SELECT 
  SUM((SELECT COUNTIF(eventInfo.eventAction = 'landing_page') FROM UNNEST(hits))) Landing_Page,
  SUM((SELECT COUNTIF(eventInfo.eventAction = 'model_selection_page') FROM UNNEST(hits) WHERE EXISTS(SELECT 1 FROM UNNEST(hits) WHERE eventInfo.eventAction = 'landing_page'))) Model_Selection  
FROM data

Notice that building this type of report in GA might be a bit more difficult as you need to select visitors who had at least fired once the event 'landing_page' and then had the event 'model_selection_page' fired. Make sure you got this report built correctly as well in your GA (one way might be to first build a customized report with only customers who had 'landing_page' fired and then apply the second filter looking for 'model_selection_page').

[EDIT]:

You asked in your comment about bringing this counting on the session and user level. For counting each session, you can limit the results to 1 for each sub-query evaluation, like so:

SELECT 
  SUM((SELECT 1 FROM UNNEST(hits) WHERE eventInfo.eventAction = 'landing_page' LIMIT 1)) Landing_Page,
  SUM((SELECT 1 FROM UNNEST(hits) WHERE EXISTS(SELECT 1 FROM UNNEST(hits) WHERE eventInfo.eventAction = 'landing_page') AND eventInfo.eventAction = 'model_selection_page' LIMIT 1)) Model_Selection  
FROM data

For counting distinct users, the idea is the same but you'd have to apply a COUNT(DISTINCT) operation, like so:

SELECT 
  COUNT(DISTINCT(SELECT fullvisitorid FROM UNNEST(hits) WHERE eventInfo.eventAction = 'landing_page' LIMIT 1)) Landing_Page,
  COUNT(DISTINCT(SELECT fullvisitorid FROM UNNEST(hits) WHERE EXISTS(SELECT 1 FROM UNNEST(hits) WHERE eventInfo.eventAction = 'landing_page') AND eventInfo.eventAction = 'model_selection_page' LIMIT 1)) Model_Selection  
FROM data