Re: DB Design question

Hi Lauri,

Thank you very much for your reply.
I, too, was thinking of something along these lines. However, it is very nice to have it confirmed by some one else independently.

Many thanks, once again.

Naran.

Lauri Pietarinen wrote:

>> 2. Every minute his program measures how busy a system is and then he
>> only wants to store the _last_ 50 of these measurements.
>
>
>
> You could try something like this:
>
> create table measurement( mes_id, mes_mod, mes_1, mes_2 etc...,
> unique(mes_id), unique(mes_mod) )
>
> insert into measurement values(1,1,0,...) -- seed row
>
> Then for each measurement you want to save do this :
>
> select max(mes_id)+1 into :max_mes_id from measurement;
> mes_mod = MOD(max_mes_id,50);
> select count(*) into :count from measurement where mes_mod = :mes_mod;
> delete from measurement where mes_mod = :mes_mod;
> insert into measurement values( :max_mes_id, mes_mod, .... );
>
> Because MOD(x,50) returns numbers 0...49 in a round robin fashion you
> will be guaranteed to have
> the 50 latest measurements in the table.
>
> I hope this is what you are looking for...
>
> regards,
> Lauri Pietarinen
>
>
>
>
Received on Fri May 16 2003 - 14:26:12 CEST