Postgres 10

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select version();

version

PostgreSQL 10.12 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 8.3.1 20190507 (Red Hat 8.3.1-4), 64-bit

create or replace function test( z int)
returns numeric as
$$
declare
x numeric(8,4):=round(z*4.1234567,2);
begin

return x;
end;

$$
language plpgsql
select * from test(1)

test

4.1200