如何为每个返回的行过滤json数组？ [英] How to filter json array per each returned row?

问题描述

我有一个带有json字段的表，用于存储对象数组。
我想查询该表，并且对于每个返回的行，通过使用某种条件对其进行过滤来仅返回json数组对象的子集。

I have a table with json field where array of objects is stored. I would like to query this table and for each returned row return only subset of json array objects by filtering them using some condition.

例如，行：

id = 1, jsonColumn = [{ field: 'abc' },{ field: 'def' },{ field: 'ghi' }]
id = 2, jsonColumn = [{ field: 'abc' },{ field: '123' },{ field: '456' }]
id = 3, jsonColumn = [{ field: 'abc' },{ field: '789' },{ field: 'XXX' }]

我想选择所有行，并且每行应在jsonColumn中仅包含元素，其中field ='abc'。我只想过滤此列，而不返回包含数组中特定元素的行...

I would like to select ALL rows, and each row should contain in jsonColumn only elements where field = 'abc'. I just want to filter this column, and NOT return rows that contain specific element in array...

推荐答案

您可以使用 json_array_elements 取消嵌套JSON， array_agg 过滤后将其嵌套。像这样的东西：

You can use json_array_elements to unnest JSON and array_agg to nest it back after filtering. Something like this:

SELECT t.id, array_to_json(array_agg(j))
FROM your_table t, json_array_elements(t.jsonColumn) j
WHERE j->>'field' = 'abc'
GROUP BY id;

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