How to update or insert an empty column with empty string column and NULL column

Can some one tell me how am I need to insert/update info or data into an empty string column and column with null as I still in the process of learning MYsql.

Any help would be appreciate :

this is the sample :
table name = product
column consist = item code, description, prices, cost, category code.
column values = 1234567 , whisky , 10.00, 8.00, "(empty column)" or "(NULL)".

I would like to update/insert the category column with alphanumeric. and update to multiple row with the where clause.

How am I to write the script?

 

I'm not sure what value you want to put in there.

It would be something like:
UPDATE product SET `category code` = 'SOME VALUE' WHERE `category code` IS NULL OR `category code` = '';

 

Thank very very much jestep, this would make my work a lot more easier then edit 1 by 1.
Thank again