why you shouldn't do ... Re: multi-valued field?

In article <5ari90$o1q_at_engnews2.Eng.Sun.COM>, tvuong_at_Eng.Sun.COM writes:
>
> > If you can flesh out the DETAILS of your OBJECTIVE in constructing a
> > 'multi valued field' perhaps we could help you find an ECONOMICAL way to
> > get what you want and 'stay true' to the ideals of the relational
> > database model...
> > ... (stuffs deleted) ...
>
> Steve,
>
> I do have a application similar to that being used by Kevin. Just
> say that the design step involving the choice of data modeling has
> already been performed by both the design and the spec team, and
> the final choice is to implement a multi-valued field as above.
> (In fact, a major influence of the decision is performance, but
> let's not get into that topic in this discussion).
>

The reason you don't want to embed logic in your data is actually for performance reasons... you typically take three shots when you embed logic:

1. front-end: must know how to insert/delete/update within the column whereas the backend would know how to handle insert/delete/update detail rows (this is true for any DBMS)
2. back-end: typically must perform a table scan to find matching rows

   Example:

       my_column = "a, b, c, d"

       Query: Find all rows that have "c"

       SQL: select ... where my_column like "%c%"

3) reporting: you *may* need to disassemble the column (as you've

   seen)...

--
Pablo Sanchez              | Ph # (415) 933.3812        Fax # (415) 933.2821
pablo_at_sgi.com              | Pg # (800) 930.5635  -or-  pablo_p_at_corp.sgi.com
===============================================================================
I am accountable for my actions.   http://reality.sgi.com/pablo [ /Sybase_FAQ ]