Google Big Query: Get New Visitor Count using Custom Dimension - google-bigquery

Question

select PARSE_DATE('%Y%m%d', t.date) as Date
,count(distinct(fullvisitorid)) as User
,SUM( totals.newVisits ) AS New_Visitors
,(if(customDimensions.index=1, customDimensions.value,null)) as Orig
FROM `table` as t
CROSS JOIN UNNEST(hits) AS hit
CROSS JOIN UNNEST(hit.customDimensions ) AS customDimensions
group by Date, orig
Is there a way to get new visitor count and use the customDimension at the same time? The sum(total.newVisits) doesn't work.
Thanks

Answer 1

Below is for BigQuery Standard SQL
SELECT DATE
,COUNT(DISTINCT(fullvisitorid)) AS User
,SUM( newVisits ) AS New_Visitors
,Orig
FROM (
SELECT PARSE_DATE('%Y%m%d', t.date) AS DATE
,fullvisitorid
,totals.newVisits AS newVisits
,(IF(customDimensions.index=1, customDimensions.value,NULL)) AS Orig
FROM `table` AS t
CROSS JOIN UNNEST(hits) AS hit
CROSS JOIN UNNEST(hit.customDimensions ) AS customDimensions
GROUP BY DATE, orig, fullvisitorid, newVisits
)
GROUP BY DATE, Orig

Answer 2

The best way in your case is to remove the cross-joins and use sub-selects instead:
SELECT
PARSE_DATE('%Y%m%d', t.date) AS Date
,(SELECT value FROM UNNEST(customDimensions) WHERE index=1) Orig
,COUNT(DISTINCT(fullvisitorid)) AS User
,SUM( totals.newVisits ) AS New_Visitors
FROM
`table` t
GROUP BY Orig, Date
In case you have a dimension on hit scope and really need to flatten the table, you need to build a session id you can count distinct. That is because you are repeating all session scoped fields on hit-scope by applying the cross-join:
SELECT
PARSE_DATE('%Y%m%d', t.date) AS Date
,(SELECT value FROM h.customDimensions WHERE index=2) justAHitCd
,h.page.pagePathLevel1
,COUNT(DISTINCT(fullvisitorid)) AS User
-- create session id and count distinct
,COUNT(DISTINCT CONCAT(fullvisitorid, CAST(visitstarttime AS STRING)) ) AS all_sessions
-- only count distinct session id of sessions where totals.newVisits = 1
,COUNT(DISTINCT
IF(totals.newVisits=1,
CONCAT(fullvisitorid, CAST(visitstarttime AS STRING)),
NULL )
) AS New_Visitors
FROM
-- flatten table to hit scope (comma means cross-join in stnd sql)
`table` t, t.hits h
GROUP BY 1,2,3
So in case for new visitors I only provide a session id if totals.newVisits=1 - else the if-statement provides NULL which is not countable.
If you have something similar on product-scope, you'd need to create an ID that takes into account session and hit.
E.g. counting pages for productSku:
SELECT
PARSE_DATE('%Y%m%d', t.date) AS Date
,(SELECT value FROM h.customDimensions WHERE index=2) justAHitCd
,p.productSku
,COUNT(DISTINCT fullvisitorid) AS users
,COUNT(DISTINCT CONCAT(fullvisitorid, CAST(visitstarttime AS STRING))) AS sessions
,COUNT(DISTINCT
IF(h.type='PAGE',
CONCAT(fullvisitorid, cast(visitstarttime AS STRING),CAST(hitNumber AS STRING)),
NULL)
) as pageviews
,COUNT(1) AS products
FROM
`table` t, t.hits h LEFT JOIN h.product p
GROUP BY 1,2,3
Note, that I'm left joining the product array. Since it sometimes is empty a cross-join would destroy all hits information: cross-join with empty table results in empty table.
Hope that helps!