BigQuery: flatten two repeated columns

Question

I am currently working with a very simple table on BigQuery and each row has two repeated columns class_numbers [REPEATED INTEGER] and class_

Answer 1

Using standard SQL, you can use UNNEST(...) WITH OFFSET. For example,

SELECT
  class_number,
  class_descriptions[OFFSET(off)] AS class_description
FROM MyTable,
  UNNEST(class_numbers) AS class_number WITH OFFSET off;

Answer 2

Below is version for BigQuery Legacy SQL

SELECT 
  class_number, 
  class_description
FROM (
    SELECT 
      class_number, 
      number_pos, 
      class_descriptions AS class_description, 
      POSITION(class_descriptions) AS description_pos 
    FROM FLATTEN((
        SELECT 
          class_numbers AS class_number, 
          POSITION(class_numbers) AS number_pos, 
          class_descriptions 
        FROM YourTable
    ), class_numbers)
)
WHERE number_pos = description_pos