Spark SQL - Return JSON Object Keys (json_object_keys)

Spark SQL function json_object_keys can be used to return an array of the outmost JSON object's keys. The input can be a valid JSON string too.

Code snippet

spark-sql> select json_object_keys('{}');
  []
spark-sql> select json_object_keys('{"key": "value"}');
  ["key"]
spark-sql> select json_object_keys('{"key1":"value1","key2":{"key3":"value3", "key4":"value4"}}');
  ["key1","key2"]

Other references

Spark SQL - Extract Value from JSON String

Spark SQL - Convert Object to JSON String