map_keys function
Applies to: 
Databricks SQL Databricks Runtime
Returns an unordered array containing the keys of map.
Syntax
map_keys(map)
Arguments
map: A MAP expression.
Returns
An ARRAY where the element type matches the map key type.
Examples
SQL
> SELECT map_keys(map(1, 'a', 2, 'b'));
[1,2]