postgres 9.6 - 从多列创建对象数组 JSON

【问题标题】：postgres 9.6 - creating array of objects JSON from multiple columnspostgres 9.6 - 从多列创建对象数组 JSON
【发布时间】：2018-12-30 05:01:07
【问题描述】：

我这里有以下数据集

http://sqlfiddle.com/#!17/70f9a/1

我想创建一个查询，结果如下：

key: 1, avg_time_1: [{ "category": 10, "avg_time": 10},{ "category": 20, "avg_time": 20 }] , avg_time_2: [{"category": 10, "avg_time": 20}, {"category": 20, "avg_time": 40}]

key: 2, avg_time_1: [{ "category": 10, "avg_time": 10},{ "category": 20, "avg_time": 60}] , avg_time_2: [{"category": 10, "avg_time": 50}, {"category": 20, "avg_time": 70}]

这个想法只是以不同的方式重新呈现值 cols avg_time_1 和 avg_time_2（jsonb 值）

【问题讨论】：

标签： postgresql aggregate-functions jsonb postgres-9.6

【解决方案1】：

使用jsonb_build_object() 构建素数对象并使用jsonb_agg() 将它们聚合成一个json数组：

select 
    key, 
    jsonb_agg(jsonb_build_object('category', category, 'avg_time', avg_time_1)) as avg_time_1,
    jsonb_agg(jsonb_build_object('category', category, 'avg_time', avg_time_2)) as avg_time_2
from data_to_agg_json
group by key

 key |                              avg_time_1                              |                              avg_time_2                              
-----+----------------------------------------------------------------------+----------------------------------------------------------------------
   1 | [{"avg_time": 10, "category": 10}, {"avg_time": 30, "category": 20}] | [{"avg_time": 20, "category": 10}, {"avg_time": 40, "category": 20}]
   2 | [{"avg_time": 10, "category": 10}, {"avg_time": 60, "category": 20}] | [{"avg_time": 50, "category": 10}, {"avg_time": 70, "category": 20}]
(2 rows)

SqlFiddle.

【讨论】：