Postgres 11

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select version();

version

PostgreSQL 11.9 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 8.3.1 20191121 (Red Hat 8.3.1-5), 64-bit

select * from json_to_record('{"reach": 240, "spend": 3.34, "clicks": 10, "frequency": 1.0375}') as x(a int, b text, d text, e text)

a
b
d
e

null
null
null
null

select * from json_to_record('{"a":1,"b":[1,2,3],"c":"bar"}') as x(a int, b text, d text)

a
b
d

1
[1,2,3]
null

select (json_populate_record(null::core_type, '{"a":1,"b":[1,2,3],"c":"bar"}'))
ERROR:  type "core_type" does not exist
LINE 1: select (json_populate_record(null::core_type, '{"a":1,"b":[1...
                                           ^

create type core_type as (id integer, tax numeric, price numeric, code varchar);
select json_populate_record(null::core_type, '{"id": "100", "tax": "4.5", "price": "10", "code": "YXCV"}')

json_populate_record

(100,4.5,10,YXCV)