yql json_query: how extract all elements of array?

[oleg68]

I want to make a query to a json column containing an array. The query should extract values of a key from all elements of array.

According to https://cloud.yandex.ru/docs/ydb/yql/reference/builtins/json the [*] and [*].key should return multiple elements.

But I cann't get it working:

$json  = cast(@@{"array":[{"key": "value1"}, {"key": "value2"}]}@@ as Json);

select
  cast(json_query($json, "$.array") as String),
  cast(json_query($json, "$.array[*]") as String),
  cast(json_query($json, "$.array[*].key") as String)

The first column returns the all elements, but the second and the third ones always return null. What is wrong in this example?