Postgres 9.5

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drop table if exists the_table cascade;

DROP TABLE

create table the_table (ob jsonb);

CREATE TABLE

insert into the_table 
values 
('{"Salary": ""}'),
('{"what is your name": ""}'),
('{"what is your lastname": ""}');

INSERT 0 3

select jsonb_object_agg(k,v)
from the_table, jsonb_each(ob) as t(k,v);

jsonb_object_agg

{"Salary": "", "what is your name": "", "what is your lastname": ""}

SELECT 1

CREATE AGGREGATE jsonb_combine(jsonb) 
(
    SFUNC = jsonb_concat(jsonb, jsonb),
    STYPE = jsonb
);

CREATE AGGREGATE

select jsonb_combine(ob)
from the_table

jsonb_combine

{"Salary": "", "what is your name": "", "what is your lastname": ""}

SELECT 1