无法使用BigQuery标准SQL拉取特定ID的“自定义维度”

Question

I came across a case where I could see value for CustomDimension1 in GA for a specific ID (CustomDimension 2). But when I pull the value from BigQuery using Standard SQL, I couldn't find the value, instead it is showing null value.

SELECT fullVisitorId, CD1, CD2
FROM (
  SELECT
    fullvisitorid, 
    (SELECT MAX(IF(index=1, value, NULL)) FROM UNNEST(hits.customDimensions)) AS CD1,
    (SELECT MAX(IF(index=2, value, NULL)) FROM UNNEST(hits.customDimensions)) AS CD2
  FROM `XXXXXXXXXXXXX`, UNNEST(hits) AS hits
)
WHERE CD2= '111111' and CD1 IS NOT NULL

Answer 1

You don't need the MAX(IF(...)) trick in standard sql, simply use a sub-select in your SELECT statement - something like (SELECT value FROM UNNEST(customDimensions) WHERE index=1) AS cd1 or in your specific case

SELECT
  fullvisitorid, visitstarttime, hitnumber,
  (SELECT cd.value
   FROM h.customDimensions AS cd
   WHERE cd.index=16 ) AS hitsCd2
FROM
  `project.dataset.ga_sessions_20171210` AS t, t.hits as h -- flatten to hits scope with cross join
LIMIT
  1000

The general approach is: First flatten to your desired dimension scope, in this case hits scope. Then calculate all the metrics - sub-selects for lower scopes and count(distinct some_id) for higher scopes.