SQL & PL/SQL

Hi,

I use Oracle 10g release2. I have following SP, which uses Execute Immediate. the problem is when I try to concatenate string literal and nvarchar2 type of variable in execute immediate. The SP compiles successfully. But give ORA-00900 error at runtime. I also tried to get generated query using dbms_output and that query runs successful. But SP is not running.

The procedure is....
CREATE OR REPLACE PROCEDURE rsp1
(
ItemID IN INT,
FieldName IN NVARCHAR2
)
AS
BEGIN
dbms_output.put_line('UPDATE Table1 SET ' || FieldName || '=null WHERE ItemID = '|| ItemID);
EXECUTE IMMEDIATE'UPDATE Table1 SET ' || FieldName || '=null WHERE ItemID = '|| ItemID;
RETURN;
END;
/

The running script is....

begin
rsp1(10,'CREATEDBY');
end;

And the output comes with error as ....
UPDATE Table1 SET CREATEDBY=null WHERE ItemID = 10
begin
*
ERROR at line 1:
ORA-00900: invalid SQL statement
ORA-06512: at "SCOTT.RSP1", line 9
ORA-06512: at line 2

This procedure works perfectly if I change the input param FieldName from nvarchar2 to varchar2 type.

Is it like Execute Immediate does not support concatenation or nvarchar2 type valriales?

Thanks,
Vivek