insertion in a table of objects with nested table in oracle - oracle

Question

I have a problem inserting in a nested table in oracle
These are the relevant types and tables;
create type movies_type as Table of ref movie_type;
create type actor_type under person_type
(
starring movies_type
) Final;
create table actor of actor_type
NESTED TABLE starring STORE AS starring_nt;
this is how i tried to insert
insert into actor values
(actor_type(29,'Carrie','Fisher',TO_DATE('21/10/1956', 'DD/MM/YY'),TO_DATE('27/12/2016', 'DD/MM/YY'),'USA', movies_type(select ref(m) from movie m where movie_id in (7, 8, 9))));
this doesn't work, it gives
SQL Error: ORA-00936: missing expression
which isn't very helpful.
i also tried nesting the select statement in parenthesis because i thought it might have been a syntax error
insert into actor values
(actor_type(29,'Carrie','Fisher',TO_DATE('21/10/1956', 'DD/MM/YY'),TO_DATE('27/12/2016', 'DD/MM/YY'),'USA', movies_type((select ref(m) from movie m where movie_id in (7, 8, 9)))));
but it said
SQL ERROR ORA-01427: single-row subquery returns more than one row
so i changed it to this
insert into actor values
(actor_type(29,'Carrie','Fisher',TO_DATE('21/10/1956', 'DD/MM/YY'),TO_DATE('27/12/2016', 'DD/MM/YY'),'USA', movies_type((select ref(m) from movie m where movie_id=7))));
which worked but it isn't what i want since it doesn't allow me to have multiple values in
movies_type
i don't understand what the problem is exactly and the errors messages aren't helpful
why does it say missing expression?
and why in the second case it gives single-row subquery returns more than one row?
thank you very much.

Answer 1

You want to use CAST and COLLECT to aggregate the references into a collection:
insert into actor values(
actor_type(
29,
'Carrie',
'Fisher',
DATE '1956-10-21',
DATE '2016-12-27',
'USA',
(
SELECT CAST( COLLECT(REF(m)) AS movies_type )
FROM movie m
WHERE movie_id IN (7, 8, 9)
)
)
);
db<>fiddle here
insert into actor values (actor_type(29,'Carrie','Fisher',TO_DATE('21/10/1956', 'DD/MM/YY'),TO_DATE('27/12/2016', 'DD/MM/YY'),'USA', movies_type(select ref(m) from movie m where movie_id in (7, 8, 9))));
why does it say missing expression?
Because you have movie_type() where the () brackets are for the object's constructor and then inside you have a SELECT statement that is nested inside another statement that is not surrounded in () brackets (as the surrounding brackets are for the constructor).
so i changed it to this
insert into actor values (actor_type(29,'Carrie','Fisher',TO_DATE('21/10/1956', 'DD/MM/YY'),TO_DATE('27/12/2016', 'DD/MM/YY'),'USA', movies_type((select ref(m) from movie m where movie_id=7))));
and why in the second case it gives single-row subquery returns more than one row?
Because, when you use WHERE movie_id IN (7,8,9) the query is returning 3 rows and it needs to return only a single row; for that you need to aggregate the multiple rows into a single row containing a collection.
what's wrong with multiple rows as parameters to the constructor?
The constructor expects a single item in each argument so you would need to use:
insert into actor values (
actor_type(
29,
'Carrie',
'Fisher',
DATE '1956-10-21',
DATE '2016-12-27',
'USA',
movies_type(
(select ref(m) from movie m where movie_id=7),
(select ref(m) from movie m where movie_id=8),
(select ref(m) from movie m where movie_id=9)
)
)
);
This would work (assuming movie_id is unique; if it isn't and things like the theatrical version and the director's cut of the same movie have the same movie_id then it still would raise exceptions) but it may use a table/index scans for each SELECT and would be less efficient than collating all the rows in a single SELECT using CAST/COLLECT.