EXECUTE IMMEDIATE ORA-01722 invalid number

Question

hi all
i have a plsql procedure in which the following statement which gives this error ORA-01722: invalid number
sql_stmt :='UPDATE Student set '||stu_gradefor||'=TO_NUMBER('||stu_marks||') where UserID='||stu_UID;
EXECUTE IMMEDIATE sql_stmt;
here all variables (stu_marks,stu_gradefor and stu_UID) are varchar2 coming from different procedure(form) but in the table named Student column HW1 (stu_gradefor) is of datatype number.
I have tried a lot but could not make it to work. Is it that we cannot enter an number through EXECUTE IMMEDIATE? If Possible can somebody help me with this?
Thanks a lot.
Regards
Jyoti

Answer 1

create table Student(UserID varchar2(8) not null, HW1 number(3) , HW2 number(3) , PA1 number(3) , ................);
create table Domain(R_Domain varchar2(11) not null, R_Status char(1) not null, R_Date Date null,R_Value varchar2(11) null, R_Mean varchar2(300) not null);
insert into Domain( R_Domain, R_Status, R_Value, R_Mean )values(
     'Term','t','PA1','First Programming Assignment');
Full names for HW1, HW2, PA1....are in the Domain table. so in variable stu_gradefor we get the R_Value.
this is true :variable stu_marks is not actually a number, so the TO_NUMBER is causing the error. stu_marks is of datatype varchar2 but the field HW1,.. are all expecting a numeric value.
i tried SELECT TO_NUMBER(stu_marks) INTO gmark FROM DUAL;
sql_stmt :='UPDATE Student set '||stu_gradefor||'=(:1) where UserID='||stu_UID;
EXECUTE IMMEDIATE sql_stmt using gmark;
where gmark is a number but noting works.same error
This can be true:the column userid is a varchar2 column with a mix of numeric and alpha numeric values. userid value that i inserted was'12345678'
i there any other way to handle this situation?
Thanks for replying
Jyoti