How to separate JSON key and value pair in Amazon Athena?

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I need help on separating JSON key and value pair. I've spent hours of googling but haven't really found a way to do this. I'm hoping to find some answers here.

So, I have a dataset here which is composed of department(string) and assets(stringified JSON) . I was able to parse the assets into a JSON and what I want to do next is to separate its key and its value (which I illustrated below).

I've tried the UNNEST but it doesn't seem to support JSON value.

How can I achieve this?

Athena Query:

WITH dataset AS 
    (SELECT 'engineering' AS department, '{"number_of_assets": {"computer": "95"}}' AS assets )
SELECT *
FROM 
    (SELECT department,
         json_extract(assets,
         '$.number_of_assets') AS number_of_assets
    FROM dataset)

Current result: enter image description here

Desired result: enter image description here

presto amazon-athena
1 Answers

You can cast your extracted json to MAP(VARCHAR, VARCHAR) (or MAP(VARCHAR, INTEGER)) and unnest the result:

WITH dataset AS (
    SELECT 'engineering' AS department,
        '{"number_of_assets": {"computer": "95"}}' AS assets
)

SELECT department, asset, count
FROM (
        SELECT department,
            cast(json_extract(assets, '$.number_of_assets') as MAP(VARCHAR, VARCHAR)) AS number_of_assets
        FROM dataset
    ) t
CROSS JOIN UNNEST(number_of_assets) AS t (asset, count);

Output:

department asset count
engineering computer 95
user_25012790
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