Error while trying to update values (cursor) - sql

Question

I'm trying to write a code which update my table base on table2.
Table1 contain column like: COLUMN1,COLUMN2,COLUMN3...
Table2 contain column 2 column:
-First column contain name of the column from the table1 which should be update
-Second contain VALUE which should be set
So Table2 output:
columnname,value
----------------
COLUMN1 , 'sometext'
COLUMN2 , 'somethingelse'
set serveroutput on;
declare cursor doupdate
is
select columnname,value from TABLE2;
nazwa TABLE2.columnname%type;
wartosc TABLE2.value%type;
begin
open doupdate;
loop
fetch doupdate into nazwa,wartosc;
exit when doupdate%notfound;
update table1 set nazwa=wartosc;
end loop;
end;
While trying to run that code I got an error message which says:
PL/SQL: ORA-00904: "NAZWA": niepoprawny identyfikator
ORA-06550: linia 12, kolumna 1:
PL/SQL: SQL Statement ignored
What I'm doing wrong? Same types of columns - Varchar2(200 bytes)
Edit. there is a problem only with NAME... Anyone know the solution?...
EDIT2. I dit it and it works fine. I used dynamically SQL so it looks like: execute immediate 'update acc SET '||nazwa||'='||wartosc; . Could anyone explain why that?:)

Answer 1

This is dynamic sql, you have to execute it with Execute immediate command:
declare
cursor doupdate
is
select columnname,value from TABLE2;
nazwa TABLE2.columnname%type;
wartosc TABLE2.value%type;
dyn_sql varchar2(500);
begin
open doupdate;
loop
fetch doupdate into nazwa,wartosc;
exit when doupdate%notfound;
dyn_sql := 'update table1 set ' || nazwa || '=' ||wartosc;
execute immediate dyn_sql
end loop;
end;
Edit
A for loop and using clause will make things much simpler.
declare
dyn_sql varchar2(500);
begin
for i in (select columnname,value from TABLE2) loop
dyn_sql := 'update table1 set ' || i.columnname || ' = :a';
execute immediate dyn_sql using i.value
end loop;
end;
bind variable (execute immediate/using) will solve your problem of smth, smth2 and 'smth, smth2'

Answer 2

Do you have a column named 'nazwa' in table1?
If you don't have, that will be the problem.
If you have, I guess that confuses the Oracle server, because it can't decide whether you think about that column or the variable named nazwa in your code. In that case you should choose another name for your variable.
Edit: maybe you're missing WHERE clause from you UPDATE.