Multiline comments are documented in the SQL Language Reference for JSON-relational Duality Views (under Restrictions) and for the GRAPHQL table function.
However, when I use it in a GraphQL table function, I get an ORA-24558: syntax error in the input string. Here's an example:
select json_serialize(data pretty) as data
from graphql('
dept
"""
This query requires a dept similar to this:
create table dept (
deptno number(2, 0) not null constraint dept_pk primary key,
dname varchar2(14 char) not null,
loc varchar2(13 char) not null
);
"""
{
_id: deptno,
dname,
loc
}
');
It works when I change it to single-line comments like this (as long as the string literal does not start with a comment):
select json_serialize(data pretty) as data
from graphql('
dept
#This query requires a dept similar to this:
#create table dept (
# deptno number(2, 0) not null constraint dept_pk primary key,
# dname varchar2(14 char) not null,
# loc varchar2(13 char) not null
#);
{
_id: deptno,
dname,
loc
}
');
IMO, this is either a documentation bug or an implementation bug.
Furthermore, it's interesting that multiline comments are not mentioned in Oracle Database Support for GraphQL Developer's Guide.