Insert into new column - Urgent

Hi there, urgent help please

I have added a new column to a table using

alter table T_LINES add
(LINE_CODE VARCHAR2(5));

I now want to populate the column, I have tried

INSERT INTO T_LINES (LINE_CODE) VALUES ('NH1')
WHERE LINE_KEY = 0;

But it keeps coming back with an error,

It's Oracle 8i on Window NT

Thanks

Alison

what you want to do is an update, not an insert !!!