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[英]Query to extract ids from a deeply nested json array object in Presto
[英]Extract complex nested JSON array in Presto
我有一个像这样的复杂 JSON 对象:
{
"item_detail": [
{
"itemid": "4702385896",
"modelid": "8307307322",
"quantity": "1"
},
{
"itemid": "3902478595",
"modelid": "8306561848",
"quantity": "1"
},
{
"itemid": "3409528897",
"modelid": "10922686275",
"quantity": "1"
},
{
"itemid": "4702385896",
"modelid": "8307307323",
"quantity": "1"
}
],
"shopid": "128449080"
},
{
"item_detail": [
{
"itemid": "7906381345",
"modelid": "9745718882",
"quantity": "1"
},
{
"itemid": "6710792892",
"modelid": "11474621623",
"quantity": "1"
}
],
"shopid": "36121097"
}
]
我正在努力将所有(itemid、shopid)提取到 Presto 中的行中。 我想要的结果是:
itemid | shopid
-----------+-------
4702385896 | 128449080
3902478595 | 128449080
3409528897 | 128449080
4702385896 | 128449080
7906381345 | 36121097
6710792892 | 36121097
我已经使用 CROSS JOIN UNNEST 和 TRANSFORM 来获得结果,但没有运气。 有没有人对此有解决方案?
非常感谢!
将json_extract
与cast
to array
和unnest
,如下所示:
presto:default> SELECT
-> json_extract_scalar(item_detail, '$.itemid') itemid,
-> json_extract_scalar(shopping, '$.shopid') shopid
-> FROM t
-> CROSS JOIN UNNEST(CAST(my_json AS array(json))) AS x(shopping)
-> CROSS JOIN UNNEST(CAST(json_extract(shopping, '$.item_detail') AS array(json))) AS y(item_detail)
-> ;
->
itemid | shopid
------------+-----------
4702385896 | 128449080
3902478595 | 128449080
3409528897 | 128449080
4702385896 | 128449080
7906381345 | 36121097
6710792892 | 36121097
(6 rows)
(在 Presto 327 上验证)
顺便说一句,如果任何数组可能为空或丢失,我建议使用LEFT JOIN UNNEST ... ON true
而不是CROSS JOIN UNNEST
(这需要一个像样的 Presto 版本):
SELECT
json_extract_scalar(item_detail, '$.itemid') itemid,
json_extract_scalar(shopping, '$.shopid') shopid
FROM t
LEFT JOIN UNNEST(CAST(my_json AS array(json))) AS x(shopping) ON true
LEFT JOIN UNNEST(CAST(json_extract(shopping, '$.item_detail') AS array(json))) AS y(item_detail) ON true;
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