postgres 9.6-从多个列创建对象JSON数组

Question

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：

键：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}]

键：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（jsonb值）重新显示cols avg_time_1和avg_time_2值

Answer 1

使用jsonb_build_object()构建主要对象，并使用jsonb_agg()将其聚合到json数组中：

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.