How do I display a nested table in Oracle - PL/SQL? - oracle

Question

I have an assignment where I'm supposed to create a user-defined function that will return all employees after 1968. My code is as follows:
First I create a new object, called emp_dobs, to hold the employees' firstname, lastname, and date of birth, using the same data types as the original employee table:
CREATE OR REPLACE TYPE emp_dobs AS OBJECT (
emp_fname VARCHAR2(20),
emp_lname VARCHAR2(20),
emp_dob DATE
);
/
Then I create emp_dobs_nested as a table of emp_dobs:
CREATE OR REPLACE TYPE emp_dobs_nested AS TABLE OF emp_dobs;
/
Lastly, I create a function that's supposed to return an emp_dobs_nested table:
CREATE OR REPLACE FUNCTION get_emp_dobs RETURN emp_dobs_nested
AS
dobs emp_dobs_nested;
BEGIN
SELECT emp_dobs(firstname, lastname, birthdate) BULK COLLECT INTO dobs
FROM employee
WHERE birthdate < TO_DATE('01-JAN-1968', 'DD-MON-YYYY');
RETURN dobs;
END;
/
There is a weird quirk with compiling emp_dob_nested, however, where Oracle SQL Developer will display a new tab labeled "Output Variables - Log," and only show EMP_FNAME and EMP_LNAME. Despite that, everything compiles.
Now I want to test the function and display its results to prove that it works, but when I try this:
DECLARE
dobs emp_dobs_nested;
BEGIN
dobs := get_emp_dobs;
DBMS_OUTPUT.PUT_LINE(dobs);
END;
/
I get this error:
Error report -
ORA-06550: line 5, column 5:
PLS-00306: wrong number or types of arguments in call to 'PUT_LINE'
ORA-06550: line 5, column 5:
PL/SQL: Statement ignored
06550. 00000 - "line %s, column %s:\n%s"
*Cause: Usually a PL/SQL compilation error.
*Action:
What am I missing here? Thanks.

Answer 1

You cannot pass the whole collection to DBMS_OUTPUT, rather you must loop through it and display individual columns at each index.
DECLARE
dobs emp_dobs_nested;
BEGIN
dobs := get_emp_dobs;
FOR i IN 1..dobs.COUNT
LOOP
DBMS_OUTPUT.PUT_LINE(dobs(i).emp_fname||','||dobs(i).emp_lname||','||dobs(i).emp_dob);
END LOOP;
END;
/

Answer 2

You can also use TABLE function to unnest a collection of objects into a relational resultset:
select * from table( get_emp_dobs )
Live demo: http://sqlfiddle.com/#!4/8cfb2/1

Answer 3

Another way of display is to use XML, try
DBMS_OUTPUT.PUT_LINE(XMLTYPE(dobs));

Answer 4

why not a create a view instead?
CREATE VIEW emp_view
AS
SELECT firstname, lastname, birthdate
FROM employee
WHERE birthdate < TO_DATE('01-JAN-1968', 'DD-MON-YYYY');
You can also try this,
DECLARE
dobs emp_dobs_nested;
i NUMBER := 0;
BEGIN
dobs := get_emp_dobs;
LOOP
i := dobs.NEXT(i);
DBMS_OUTPUT.PUT_LINE(dobs(i).emp_fname||','||dobs(i).emp_lname||','||dobs(i).emp_dob);
IF i = dobs.LAST THEN
EXIT;
END IF;
END LOOP;
END;
/