I have an array of maps and data format is ARRAY(MAP(VARCHAR, VARCHAR)); I'd like to extract "id" and "description" features from this "Item_Details" column:

 ----------- ------------- ------------------------------------------------------------------------------------------------------------------------------------------------------------ -- -- 
| Company   | Country     | Item_Details                                                                                                                                               |  |  |
 =========== ============= ============================================================================================================================================================ == == 
| Apple     | US          | [{"created":"2019-09-15","product":"apple watch", "amount": "$7,900"},{"created":"2022-09-19","product":"iPhone", "amount": "$78,300"},{"created":"2021-01-13","product":"Macbook Pro", "amount": "$163,980"}] |  |  |
| Google    | US          | [{"created":"2020-07-15","product":"Nest", "amount": "$78,300"},{"created":"2021-07-15","product":"Google phone", "amount": "$178,900"}]                             |  |  |
 ----------- ------------- ------------------------------------------------------------------------------------------------------------------------------------------------------------ -- 

My expected outputs would be:

 ----------- ------------- ------------------------------------------------------------------------------------------------------------------------------------------------------------ -- -- 
| Company   | Country     | Item_Details                                                                                                                                               |  |  |
 =========== ============= ============================================================================================================================================================ == == 
| Apple     | US          | ["product":["apple watch", "iPhone", "Macbook Pro"], "amount":[ "$7,900", "$78,300","$163,980"] |  |  |
| Google    | US          | ["product":["Nest", "Google phone"], "amount": "$78,300", "$178,900"]                             |  |  |
 ----------- ------------- ------------------------------------------------------------------------------------------------------------------------------------------------------------ -- 

or

 ----------- ------------- ------------------------------------------------------------------------------------------------------------------------------------------------------------ -- -- 
| Company   | Country     | Product    | Amount                                                                                                                                               |  |  |
 =========== ============= ============================================================================================================================================================ == == 
| Apple     | US          | apple watch | $7,900   |  |  |
| Apple     | US          | iPhone      | $78,300  |  |  |
| Apple     | US          | Macbook Pro | $163,980 |  |  |
  ...
 ----------- ------------- ------------------------------------------------------------------------------------------------------------------------------------------------------------ -- 

I tried element_at(Item_Details, 'product') and json_extract_scalar(Item_Details, '$.product') but received error "Unexpected parameters (array(map(varchar,varchar)), varchar(23)) for function element_at. "

Any suggestions is much appreciated! Thank you in advance

CodePudding user response：

For the second one you can unnest the array and access elements of map:

-- sampel data
WITH dataset(Company, Country, Item_Details) AS (
    values ('Google', 'US', array[
        map(array['created', 'product', 'amount'], array['2019-09-15', 'Nest', '$78,300']),
        map(array['created', 'product', 'amount'], array['2019-09-16', 'Nest1', '$79,300'])
    ])
)

-- query
select Company,
       Country,
       m['product'] product,
       m['amount'] amount
from dataset d,
unnest(Item_Details) as t(m);

Output: