Dynamic select execution missing expression error - oracle

Question

I am using Oracle 12, and I want to make a dynamic procedure which selects rows from specific table but according to an unknown conditio. That condition will be specified as input parameter.
Suppose I have a column called employee id and I want to call the procedure
with the following condition
execute s('employeeid = 2')
My code is
create or replace procedure s (condition varchar)
as
TYPE EmpCurTyp IS REF CURSOR; -- define weak REF CURSOR type
emp_cv EmpCurTyp; -- declare cursor variable
my_ename VARCHAR2(15);
my_sal NUMBER := 2;
mycondition varchar2(100):=condition;
BEGIN
OPEN emp_cv FOR -- open cursor variable
'SELECT employeeid, employeename FROM employees WHERE = :s' USING mycondition;
END;
but I am getting an error
missing expression
What am I doing wrong, and will the result of this procedure be selected rows from employees table that satisfy applied condition ?

Answer 1

The USING is meant to handle values, not pieces of code; if you need to edit your query depending on an input parameter ( and I believe this is a very dangerous way of coding), you should treat the condition as a string to concatenate to the query.
For example, say you have this table:
create table someTable(column1 number)
This procedure does somthing similar to what you need:
create or replace procedure testDyn( condition IN varchar2) is
cur sys_refcursor;
begin
open cur for 'select column1 from sometable where ' || condition;
/* your code */
end;
Hot it works:
SQL> exec testDyn('column1 is null');
PL/SQL procedure successfully completed.
SQL> exec testDyn('column99 is null');
BEGIN testDyn('column99 is null'); END;
*
ERROR at line 1:
ORA-00904: "COLUMN99": invalid identifier
ORA-06512: at "ALEK.TESTDYN", line 4
ORA-06512: at line 1

Answer 2

This is not embedded in a procedure yet but I tested this and works:
DECLARE
TYPE OUT_TYPE IS TABLE OF VARCHAR2 (20)
INDEX BY BINARY_INTEGER;
l_cursor INTEGER;
l_fetched_rows INTEGER;
l_sql_string VARCHAR2 (250);
l_where_clause VARCHAR2 (100);
l_employeeid VARCHAR2 (20);
l_employeename VARCHAR2 (20);
l_result INTEGER;
o_employeeid OUT_TYPE;
o_employeename OUT_TYPE;
BEGIN
l_cursor := DBMS_SQL.OPEN_CURSOR;
l_sql_string := 'SELECT employeeid, employeename FROM employees WHERE ';
l_where_clause := 'employeeid = 2';
l_sql_string := l_sql_string || l_where_clause;
DBMS_SQL.PARSE (l_cursor, l_sql_string, DBMS_SQL.V7);
DBMS_SQL.DEFINE_COLUMN (l_cursor,
1,
l_employeeid,
20);
DBMS_SQL.DEFINE_COLUMN (l_cursor,
2,
l_employeename,
20);
l_fetched_rows := 0;
l_result := DBMS_SQL.EXECUTE_AND_FETCH (l_cursor);
LOOP
EXIT WHEN l_result = 0;
DBMS_SQL.COLUMN_VALUE (l_cursor, 1, l_employeeid);
DBMS_SQL.COLUMN_VALUE (l_cursor, 2, l_employeename);
l_fetched_rows := l_fetched_rows + 1;
o_employeeid (l_fetched_rows) := l_employeeid;
o_employeename (l_fetched_rows) := l_employeename;
l_result := DBMS_SQL.FETCH_ROWS (l_cursor);
END LOOP;
DBMS_SQL.CLOSE_CURSOR (l_cursor);
DBMS_OUTPUT.PUT_LINE (o_employeeid (1));
DBMS_OUTPUT.PUT_LINE (o_employeename (1));
EXCEPTION
WHEN OTHERS
THEN
DBMS_OUTPUT.PUT_LINE ('GENERAL FAILURE: ' || SQLERRM);
END;