Re: 4 the FAQ: Are Commercial DBMS Truly Relational?

"Laconic2" <laconic2_at_comcast.net> wrote:

[snip]

>Another one:
>
>We have 30,000 addresses, but they all have COUNTRY = 'USA' in them. There
>is a query that
>specifies the state, city, and zip code, but doesn't specify the country.
>After all, why specify the country, when it's always 'USA' in this
>database? The query scans the index. We add the specification COUTRY =

     But does the DBMS know that? If it does not, it has to make sure, just in case.

>'USA' to the WHERE clause, and all of a sudden it uses the index for
>lookup, which runs much faster.
>
>Can you figure out why each of these got sped up?
>Hint: think about compound index keys.
>
>Maybe these cases are much too simple to post in here, but back when I was
>making the big bucks, this is the sort of thing that made customers
>grateful!

     Often, the solution is rather simple when using the/a right approach. Doing it the wrong way can have such complications.

Sincerely,

Gene Wirchenko

Computerese Irregular Verb Conjugation:

     I have preferences.
     You have biases.
     He/She has prejudices.