Scripting question

I am running insert statement against the database using the following script:

 
sqlplus 'username/pwd@MYDB' << EOF > $FILE1
                        whenever sqlerror exit 1 rollback
                        $sql
                        commit;
                        exit;
EOF
res=$?
if [ "$res" != "0" ]
then
echo error 
fi

For some reason $res returns 1 instead of 0 even though the data gets inserted into the database and no error is written to the error log

Why the code returns 1, am I doing something wrong?