cars, PostgreSQL - rextester

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CREATE TABLE vch
    (vchid int4, subject text);    
INSERT INTO vch
    (vchid, subject)
VALUES
    (1, 'Volvo'),
    (2, 'Ford'),
    (3, 'Jeep'),
    (4, 'Toyota');

CREATE TABLE rec
    (recid int4, recvch int4, recname text);    
INSERT INTO rec
    (recid, recvch, recname)
VALUES
    (1000, 1,'xxx'),
    (2000, 1,'yyy'),
    (3000, 3,'zzz'),
    (4000, 4,'aaa');

select unnest(string_to_array(
                  (vchid::text || ' ' || subject
                  || ',{'::text
                  || ',' 
                  || (select string_agg(format(e'%s %s', rec.recid, rec.recname), ',')
                     from rec where vch.vchid = rec.recvch)::text                     
                  || ',}'::text)::text
                  , ',')) result
from vch;

select string_agg(f, chr(10)) as result
from (select unnest(string_to_array(
                  (vchid::text || ' ' || subject
                  || ',{'::text
                  || ',' 
                  || (select string_agg(format(e'%s %s', rec.recid, rec.recname), ',')
                     from rec where vch.vchid = rec.recvch)::text                     
                  || ',}'::text)::text
                  , ',')) f
from vch) a
;


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