Postgresql 合并/聚合 json 列并返回 json 对象作为输出

Question

I am using Postgresql 9.6

I have a table, where my column is of type json.

create table test (
my_data json,
.
.
);

When queried, for each row the column is shown as json:

I want to aggregate the data, for sake of simplicity selected 2 columns only. I need to group by col1_data. I want like below:

I tried to use json_agg, but that will agregate and output as array of jsons.

select col1_data, json_agg(col2_data) as col2_data
from test
group by col1_data;

Can someone help to convert the array of json to json?

Answer 1

This should do it:

select col1_data, json_agg(col2_element) as col2_data
from test, json_array_elements(col2_data) as col2_element
group by col1_data;

Alternatively, you can write your own aggregate function that concatenates json arrays.