BigQuery Error - Uncategorized name - When combining GA data - sql

Question

I want to combine dimensions date, country & source with sessions and unique events for event category "Downloads". Based on this data, I want to calculate the Download Conversionrate in DataStudio later on. To be honest I'm a noob in SQL. But I hope I'm thinking the right way at least.
Trying the query below I get the following error:
Unrecognized name: Downloads at [40:3]
WITH
ga_tables AS (
SELECT
date,
trafficSource.source AS Source,
geoNetwork.country AS Country,
COUNT ( trafficSource.source ) AS Sessions
FROM
`xxxxxx.ga_sessions_*`
WHERE
_TABLE_SUFFIX BETWEEN '20190301'
AND '20190301'
GROUP BY
date,
Source,
Country
UNION ALL
SELECT
date,
trafficSource.source AS Source,
geoNetwork.country AS Country,
COUNT(DISTINCT CONCAT(CAST(fullVisitorId AS string),'-',CAST(visitId AS string),'-',CAST(date AS string),'-',ifnull(hits.eventInfo.eventLabel,
'null'))) AS Downloads
FROM
`xxxxxx.ga_sessions_*`,
UNNEST(hits) AS hits
WHERE
_TABLE_SUFFIX BETWEEN '20190301'
AND '20190301'
AND hits.type = 'EVENT'
AND hits.eventInfo.eventCategory = 'Downloads'
GROUP BY
date,
Source,
Country )
SELECT
date,
Country,
Source,
Downloads,
Sessions
FROM
ga_tables
ORDER BY
Sessions ASC

Answer 1

In your with statement, the fourth column in the first select statement is named Sessions, while the fourth column in the statement it's unioned with is called Downloads. Due to the nature of UNION ALL, the final output column will be called Sessions, so it does not exist when you are querying it. If you want Sessions and Downloads to be separate columns, make the query look something like this:
WITH
ga_tables AS (
SELECT
date,
trafficSource.source AS Source,
geoNetwork.country AS Country,
COUNT ( trafficSource.source ) AS Sessions,
NULL AS Downloads
FROM
`xxxxxx.ga_sessions_*`
WHERE
_TABLE_SUFFIX BETWEEN '20190301'
AND '20190301'
GROUP BY
date,
Source,
Country
UNION ALL
SELECT
date,
trafficSource.source AS Source,
geoNetwork.country AS Country,
NULL AS Sessions,
COUNT(DISTINCT CONCAT(CAST(fullVisitorId AS string),'-',CAST(visitId AS string),'-',CAST(date AS string),'-',ifnull(hits.eventInfo.eventLabel,
'null'))) AS Downloads
FROM
`xxxxxx.ga_sessions_*`,
UNNEST(hits) AS hits
WHERE
_TABLE_SUFFIX BETWEEN '20190301'
AND '20190301'
AND hits.type = 'EVENT'
AND hits.eventInfo.eventCategory = 'Downloads'
GROUP BY
date,
Source,
Country )
Edit: Given what it looks like you want to do with the table though, you might want to rewrite ga_tables to be something like this instead:
WITH
ga_tables AS (SELECT
date,
trafficSource.source AS Source,
geoNetwork.country AS Country,
MAX(Sessions) AS Sessions,
COUNT(DISTINCT CONCAT(CAST(fullVisitorId AS string),'-',CAST(visitId AS string),'-',CAST(date AS string),'-',ifnull(hits.eventInfo.eventLabel,
'null'))) AS Downloads
FROM (
SELECT
*,
COUNT(trafficSource.source) OVER (PARTITION BY date, Source, Country) AS Sessions
FROM
`xxxxxx.ga_sessions_*`),
UNNEST(hits) AS hits
WHERE
_TABLE_SUFFIX BETWEEN '20190301'
AND '20190301'
AND hits.type = 'EVENT'
AND hits.eventInfo.eventCategory = 'Downloads'
GROUP BY
date,
Source,
Country)