i think is your system operating system firewall is on.so 
you off the firewall.
 And  if in ur system installed any antivirus softwares 
then u check antivirus firewall is off.

 first u check oracle client database is connecting is 
correct  through network. 

above the process do to server and client systems. ok..

virus means very important resource under seize
it is a programm written by some one which makes ur system 
corrupt

virus means veary importemt resource under seize tit is a 
program written by some one which makes ur system corrupt

insert into abc.tablename(select * from xyz)here xyz is
database1 abc is tempory database but here u select database
is xyz then only this query is excuted if u any doubt mail
me yhis is my mail id laxmanit08@gmail.com 
any query u wnt just send a msg ok bye tc



laxman

CREATE TABLE Sample
(
Col1 varchar(5)
)
insert into Sample values('j')

TABLE:
Col1
j
r
c
r
e
f
g
h
x
j

USING CURSOR: ANSWER

DECLARE @COL1 VARCHAR(5)
DECLARE @COUNT VARCHAR(5)
SET @COUNT=0
DECLARE c1 CURSOR
FOR
SELECT COL1 FROM SAMPLE
OPEN C1
FETCH NEXT FROM C1
INTO @COL1
WHILE @@FETCH_STATUS=0
BEGIN
SET @COUNT=@COUNT+1
IF @COUNT>=5
BEGIN
SELECT @COL1
END
FETCH NEXT FROM C1
INTO @COL1
END
CLOSE C1
DEALLOCATE C1

create table empmaster(ename  varchar(34))

insert into empmaster values('r')

select * from empmaster

Query: 

select top 6 (ename) from empmaster order by ename desc

select * from table_name limit 6;
above query is wrkg in mysql 
ex;
select * from emp limit 6;
this one is upto 6
u want 10 limit 10 ;
thts ur choice

select * from emp columnname limit 6;
ok

If this is the only error message, you should stop trying to
modify a system table (table owned by sys), as this is not
allowed.

sys admin is the only authorized one can drop or alter the 
table , others can't make any changes.

Cause:  An attempt was made to drop a column from a system
table.
Action: This action is not allowed

Does not commit your changes, because this table is SYS 
schema's table

Dont have the permission to midify the Database Object

Cause: A syntax error was detected in the comment.

Action: Use '--' only when specifying the end of the comment.

Please add more information about this Error

Cause: Attribute default was invalid.

Action: Default must be REQUIRED, IMPLIED, or FIXED.

Please add more information about this Error

Cause: A syntax error was detected.

Action: Use proper syntax.

Please add more information about this Error

Cause: Processing instruction starting with XML was found.

Action: Use another name for the processing instruction.

Please add more information about this Error

Cause: An unknown keyword was found in the DTD.

Action: Use a proper keyword.

Please add more information about this Error