Should I create an enumeration or individual flags? I'm creating a new database table which will be used to store pictures of products. I'd like to identify the product "type" represented in the picture.  Say we have 3 general categories for all the products:


tables,
chairs,
and lamps.


Am I better off creating 3 boolean columns, is_table, is_chair, and is_lamp?

Or am I better off creating an enumeration, and then using a single column for that enum:

CREATE TYPE product_type AS ENUM ('table', 'chair', 'lamp' );


(Note that with the engineering product pictures we're storing, it is guaranteed a product/picture will never qualify as 2 types.  It must always be 1 very specific type.)
You should normalize this and create a reference table, that way you can use a simple data type for the type indicator and also be future proof if you need to add types. It also makes for easier queries, plus this structure will maintain the constraint of each product only being of one type at a time.

so (assuming this is an Oracle db):

   Create table Product_types 
   (id int,
    name varchar2(100),
    constraint pk_product_types primary key  (id)
    );

create table products 
    (id int, 
     product_type int, 
     somecolumn varchar2(100),
     anothercolumn varchar2(100),
     somedatecolumn date,
     constraint fk_products_product_type foreign key (product_type) references product_types(id)
     );