[thelist] SQL : performance - separate table vs. (datatype) SET
Hassan Schroeder
hassan at webtuitive.com
Wed Nov 13 09:36:01 CST 2002
jerryscannell at cox.net wrote:
> In general, it isn't a good idea to have "set" field types that
> you will perform "like" type clauses.
> (2) an ingredients column using the SET datatype to include all
> ingredients -- ingredients SET("milk","butter","eggs") -- and
> search them via something like
>
> WHERE ingredients LIKE "%milk%eggs%"
>
> not sure that's how you search a set
Ah, since I posted that I discovered that rudy was right -- that's
*not* the way to search a set, you use the numeric mask, making the
example above
WHERE ingredients = 5;
So using that presumably lighter approach, does your comment
> The overhead relative to searching for such a data set is enormous.
still apply?
And if so, if SETs are inherently inefficient, why do they exist?
What problem were they created to solve? When *should* they be used?
Inquiring minds want to know!
TIA!
--
Hassan Schroeder ----------------------------- hassan at webtuitive.com
Webtuitive Design === (+1) 408-938-0567 === http://webtuitive.com
dream. code.
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