Postgres 10

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CREATE TABLE ttable 
(
  tcol numeric,
  constraint check_tcol_scale check (scale(tcol) <= 4)
);

CREATE TABLE


-- this fails
insert into ttable values (123.45678);

ERROR:  new row for relation "ttable" violates check constraint "check_tcol_scale"
DETAIL:  Failing row contains (123.45678).


-- this succeeds
insert into ttable values (123.4567);

INSERT 0 1