Re: Table design - unknown number of column

I think the typical way of attacking a problem would be a second and third
table. The second table would look like:

flat_type table
flag_type_id
flag_type (like the column name in your original table)
flag_type_description (BONUS: you can describe each flag)

product_flag table
product_id (fk to your original table)
flag_type_id (fk to the flag_type table)
flag_value (0, 1, or whatever you want to store here)

The advantages with this method are several:
1) No wasted storage for all those NULLs where a flag is not needed
2) Should be very fast to lookup by product_id to get all flags
3) You can expand to an arbitrary number of flags
4) Your schema remains normalized

Sean