Can I merge sketches present in 2 different columns in Google BigQuery

Question

If i have 2 columns with sketches made on the same datatype, can i merge the sketches in both columns to get a final sketch corresponding to each row in the dataset in Google BigQuery?

col1 | col2 | sketchA|sketchB
_______________________________
c1  | c2    |sketch1 | sketch5
c3  |  c4   |sketch2 | null
c3  | c5    |sketch3 | null
c3  |c6     |null.   |sketch6
c2  |c6     |sketch7 |  sketch4
c5  |c9     |null    |sketch8

is it possible to merge sketch columns => sketchA, sketchB ? such that the final output is

col1 | col2 | sketchMerge
___________________
c1  | c2    |merge(sketch5, sketch1)
c3  |  c4   |sketch2
c3  | c5    |sketch3
c3  |c6     |sketch6
c2  |c6     |merge(sketch7, sketch4)
c5  |c9     |sketch8

Answer 1

Yes, you can. Use below approach (BigQuery Standard SQL)

SELECT *, (
  SELECT HLL_COUNT.MERGE_PARTIAL(sketch)
  FROM UNNEST([sketchA, sketchB]) sketch
) AS sketchMerge
FROM your_table

If apply to dummy data similar to yours in question - output is