Question

这是我正在查询的JSON对象：

const data =
{"fruit":["apple"],"vegetables":["carrot","turnip"],"dairy":["milk","cheese"]}'

这就是我要在postgres表中返回的内容：

  category   | item
--------------------
  fruit      |  apple 
  vegetables |  carrot
  vegetables |  apple 
  dairy      |  milk
  dairy      |  cheese

这是我到目前为止要做的：

SELECT key as category, value as item
FROM json_each_text('${data}')

  category   | item
--------------------
  fruit      |  ["apple"] 
  vegetables |  ["carrot", "turnip"]
  dairy      |  ["milk", "cheese"]

有人知道如何取消嵌套/将item列中的值扩展到新行吗？谢谢：）

Answer 1

你非常亲密。

只需使用json_array_elements_text从json数组中提取项目：

SELECT key as category, json_array_elements_text(value::json) as item
FROM json_each_text('{"fruit":["apple"],"vegetables":["carrot","turnip"],"dairy":["milk","cheese"]}'::json);
  category  |  item  
------------+--------
 fruit      | apple
 vegetables | carrot
 vegetables | turnip
 dairy      | milk
 dairy      | cheese
(5 Zeilen)

如果其他类型的数组遇到此问题，请考虑使用UNNEST：

SELECT UNNEST(ARRAY['foo','bar']);
 unnest 
--------
 foo
 bar
(2 Zeilen)

SELECT UNNEST('{"foo","bar"}'::TEXT[]);
 unnest 
--------
 foo
 bar
(2 Zeilen)

查询JSON嵌套数组并扩展到Postgres表中的多行

1 个答案: