How to extract all the keys in a JSON object with BigQuery

Question

BigQuery has facilities to parse JSON in real-time interactive queries: Just store the JSON encoded object as a string, and query in real time, with functions like JSON_EXTR

Answer 1

Here's something that uses Standard SQL:

CREATE TEMP FUNCTION jsonObjectKeys(input STRING)
RETURNS Array
LANGUAGE js AS """
  return Object.keys(JSON.parse(input));
""";
WITH keys AS (
  SELECT
    jsonObjectKeys(myColumn) AS keys
  FROM
    myProject.myTable
  WHERE myColumn IS NOT NULL
)
SELECT
  DISTINCT k
FROM keys
CROSS JOIN UNNEST(keys.keys) AS k
ORDER BY k