If the two tables are always or almost always used in combination, then it
makes sense (and from a realtional theory point of view as well) to combine
into one big one. In fact, if, from a realtional theory viewpoint they
should be combined, then definitely do so (in this case).
"Steffen Ramlow" <s.ramlow_at_gmx.de> wrote in message
news:a8hm7r$sqgtj$1_at_ID-54600.news.dfncis.de...
> what r the advantages / disadvantages of this?
>
> sample:
>
> Main (pk, id, c1, c2)
> Sub1 (pk1, fk1, c10, c11)
> Sub2 (pk2, fk2, c20, c21)
>
> rows:
>
> Main: 1,1,2,3
> Sub1: 1,1,4,5
> Sub2: 1,1,6,7
>
> vs.
>
> BigMain(pk,id,c1,c2,c10,c11,c20,c21)
>
> rows:
>
> 1,1,2,3,4,5,null,null
> 2,1,2,3,null,null,6,7
>
>
> the rows are always read as when Main and Subx would be inner joined
>
> obvious is, that BigMain has many null values (there are up to 10 sub
> tables) but u do not need to join Main and Subx
>
> i would use Main + Sub, coz it is better to maintain and to tune, but what
> about the costs of the join?
>
> both tables may contain millions of rows
>
> what r ur options?
>
>
>
Received on Thu Apr 04 2002 - 08:49:02 CST
