Open cur for .. using

Question

Hi,
my stmt does not give me any results and i don't how to find the error. It must have to do with the using clause as the statement works, if i call it directly.
  procedure p_get_unique_key
     p_owner varchar2
   , p_table_name varchar2
  IS
    v_count int;
    v_query varchar2(500);
    curid int;
    Type cols IS TABLE OF varchar2(2500);
    v_uk_columns cols;
    TYPE curtype IS REF CURSOR;
    cur      curtype;
  BEGIN
    v_query := '
    select cc.column_name
    from all_constraints c
    join all_cons_columns cc
       on cc.owner = c.owner
      and cc.constraint_name = c.constraint_name
    where c.constraint_type = ''U''
      and c.owner = :1
      and c.table_name = :2  
    dbms_output.put_line(v_query);
    open cur for v_query
    using p_owner, p_table_name;
    FETCH cur BULK COLLECT INTO v_uk_columns;
    DBMS_OUTPUT.PUT_LINE(v_uk_columns.COUNT);
    close cur;
  END;
  Who can help me?
Tobe

Answer 1

Why are you using a ref cursor? There is no need for it. Why are you even using a cursor at all in the 1st place when you doing a single (no-loop) fetch?
When you write code, you need to have justification for why you wrote what you did. To do that, you need to know exactly what each line of code you write does - and knowing that, you can make the call whether that line of code does what is required or not. And to be honest, your code is pretty messy as it uses superfluous concepts (why subtype a ref cursor when you can instead use the sys_refcursor type?) and incorrect and complex approaches (using an explicit ref cursor with manual binding when an implicit cursor is easier).
For example (and note the proper use of programming language syntax standards regarding pascalcase and camelcase):
create or replace procedure DoSomethingWithUniqueKey( keyOwner varchar2, tableName varchar2 ) is
  -- not sure why you call it GetUniqueKey as you parameter signature fails to return/get anything for the caller
  type TStrings is table of varchar2(4000);
  colList TStrings;
  ...  other stuff
begin
  .. other stuff
  select
        cc.column_name bulk collect into ColList
  from all_constraints c
  join all_cons_columns cc
     on cc.owner = c.owner
    and cc.constraint_name = c.constraint_name
  where c.constraint_type = 'U'
    and c.owner = upper(keyOwner)
    and c.table_name = upper(tableName);
    .. other stuff   
end;Compare the number of lines and readability and maintainability of your code with this.