Does Oracle support non-scalar cursor parameter? - plsql

Question

This is a question about Oracle PL/SQL.
I have a procedure in which the exact WHERE clause is not known until the run time:
DECLARE
CURSOR my_cursor is
SELECT ...
FROM ...
WHERE terms in (
(SELECT future_term2 FROM term_table), -- whether this element should be included is conditional
(SELECT future_term1 FROM term_table),
(SELECT present_term FROM term_table)
);
BEGIN
(the processing)
END;
/
What the (SELECT ... FROM term_table) query returns is a 4-character string.
For a solution to this, I am thinking of using a parameterized cursor:
DECLARE
target_terms SOME_DATATYPE;
CURSOR my_cursor (pi_terms IN SOME_DATATYPE) IS
SELECT ...
FROM ...
WHERE terms in my_cursor.pi_terms;
BEGIN
target_terms := CASE term_digit
WHEN '2' THEN (
(SELECT future_term2 FROM term_table),
(SELECT future_term1 FROM term_table),
(SELECT present_term FROM term_table)
) ELSE (
(SELECT future_term1 FROM term_table),
(SELECT present_term FROM term_table)
)
END;
FOR my_record IN my_cursor (target_terms) LOOP
(the processing)
END LOOP;
END;
/
The problem is what the datatype for SOME_DATATYPE should be is not known to me, nor is it known whether Oracle supports such a cursor parameter at all. If supported, is the way shown above to fabricate the value for target_terms correct? If not, how?
Hope someone who know can advise. And thanks a lot for the help.

Answer 1

You can certainly pass a parameter to a cursor, just like you can to a function - but only IN parameters. However, PL/SQL is a strongly typed language, so the datatype must be specified at the time of compilation.
It looks to me like what you will need to do is construct the query dynamically and then use
OPEN cursor FOR l_query;
where l_query is the constructed string. This should give you a feel for what you can do:
CREATE OR REPLACE PACKAGE return_id_sal
AUTHID DEFINER
IS
TYPE employee_rt IS RECORD
(
employee_id employees.employee_id%TYPE,
salary employees.salary%TYPE
);
FUNCTION allrows_by (append_to_from_in IN VARCHAR2 DEFAULT NULL)
RETURN SYS_REFCURSOR;
END return_id_sal;
/
CREATE OR REPLACE PACKAGE BODY return_id_sal
IS
FUNCTION allrows_by (append_to_from_in IN VARCHAR2 DEFAULT NULL)
RETURN SYS_REFCURSOR
IS
l_return SYS_REFCURSOR;
BEGIN
OPEN l_return FOR
'SELECT employee_id, salary FROM employees ' || append_to_from_in;
RETURN l_return;
END allrows_by;
END return_id_sal;
/
DECLARE
l_cursor SYS_REFCURSOR;
l_row return_id_sal.employee_rt;
BEGIN
l_cursor := return_id_sal.allrows_by ('WHERE department_id = 10');
LOOP
FETCH l_cursor INTO l_row;
EXIT WHEN l_cursor%NOTFOUND;
END LOOP;
END;
/
You will need to take precautions against SQL injection with this sort of code. Certainly a user should never be able to pass SQL text directly to such a function!

Answer 2

You can use also some built-in VARRAY SQL types like SYS.ODCIVARCHAR2LIST or create your own :
CREATE OR REPLACE NONEDITIONABLE TYPE VARCHARLIST
AS VARRAY(32767) OF VARCHAR2(4000);
Then you can use it with SELECT COLUMN_VALUE FROM TABLE(COLLECTION) statement in your cursor:
DECLARE
l_terms SYS.ODCIVARCHAR2LIS; --or VARCHARLIST
CURSOR my_cursor (p_terms IN SYS.ODCIVARCHAR2LIS) IS
SELECT your_column
FROM your_table
WHERE terms in (select COLUMN_VALUE from table (p_terms));
BEGIN
select term
bulk collect into l_terms
from (
select 'term1' term from dual
union all
select 'term2' term from dual
);
FOR my_record IN my_cursor (l_terms) LOOP
--process data from your cursor...
END LOOP;
END;