problem with table structure

Miguel Vaz <pagongski@gmail.com> wrote:

[...]
* sites (generic):

id_site
name
description
x
y

* site_natural
id
id_site
altitude

* site_arqueology
id
id_site
id_category
id_period

But i seem to be missing something. How can i have this in a way that its
easy to list only "arqueology sites" for example. I feel the solution is
simple enough, even for me, but its eluding me. Any help in the right
direction would be very appreciated.

You mean archaeological sites that are not also natural
sites?

| SELECT * FROM site_arqeuology
| WHERE id_site NOT IN
| (SELECT id_site FROM site_natural);

There are numerous other ways to do this, i. e., with "LEFT
JOIN", "EXCEPT", etc.

Tim

Hi, Tim,
I was looking for an opinion on the actual table structure. :-) How should i
build the data set? Is my second example ok? The first is the long version
but i wanted to put together all the common fields to both types of "sites"
and then (maybe) build tables to accomodate the specific fields so there are
no empty columns on the table if i put everything in the same table.

Pag

On Fri, Jul 9, 2010 at 10:30 AM, Tim Landscheidt <tim@tim-landscheidt.de>wrote:

On 9 Jul 2010, at 3:41, Miguel Vaz wrote:

and i would like to put these two "sites" in the same data set and maybe add a new table called "site types" to categorize each record (maybe a relation table to allow many to many): how can i go about doing it? is this solution decent enough:

* sites (generic):

id_site
name
description
x
y

* site_natural
id
id_site
altitude

* site_arqueology
id
id_site
id_category
id_period

But i seem to be missing something. How can i have this in a way that its easy to list only "arqueology sites" for example. I feel the solution is simple enough, even for me, but its eluding me. Any help in the right direction would be very appreciated.

That design seems fine to me. I'd probably put unique constraints on site_natural.id_site and site_arqueology.id_site to fix those into a 1:1 relationship with site.id, otherwise it would allow data with a 1:n relationship - multiple natural or archeological sites at the same location and name.

Another possibility is to use table inheritance, but be aware that some things can't be inherited (foreign key constraints, for example).

BTW, shouldn't that table be named site_archeological? Or if arquelogy is Spanish or Portuguese, shouldn't it be arquelogical?

Alban Hertroys

--
Screwing up is an excellent way to attach something to the ceiling.

!DSPAM:737,4c370742286211218711353!

Miguel Vaz <pagongski@gmail.com> wrote:

I was looking for an opinion on the actual table structure. :-) How should i
build the data set? Is my second example ok? The first is the long version
but i wanted to put together all the common fields to both types of "sites"
and then (maybe) build tables to accomodate the specific fields so there are
no empty columns on the table if i put everything in the same table.
[...]

That's way too fuzzy for good advice. Few people build data
sets on archaeological sites, and even those probably don't
use all the same structure.

Tim
(not telepathic)

Thank you for the opinion, Alban. The names are the least of my worries, i
typed them without thinking. And its portuguese. :-)

If, using that design, i had a different table with something like arq_types
{ id_arq_type, descr } that i could somehow connect to the generic table
(the one with the common fields), how could i go about querying those tables
for all the results of a specific type, for example? Or maybe i could add a
"table_name" field on that arq_type table?

Tim:

Dont consider this to be strictly for archeology, i mean in a generic sense
that if we have several data sets with common fields, if we could divide
them into several tables, one with common fields, and the others with fields
related to each type. My doubt was regarding how to have a separate table
with "types" that could be used to help query the "common fields table" and
fetch the corresponding table of that specific type. I understand its a bit
ungrateful for you guys to understand what i mean, considering that i am
probably making things even more confusing. :-)

Pag

On Fri, Jul 9, 2010 at 1:47 PM, Tim Landscheidt <tim@tim-landscheidt.de>wrote:

On 9 Jul 2010, at 17:08, Miguel Vaz wrote:

Thank you for the opinion, Alban. The names are the least of my worries, i typed them without thinking. And its portuguese. :-)

If, using that design, i had a different table with something like arq_types { id_arq_type, descr } that i could somehow connect to the generic table (the one with the common fields), how could i go about querying those tables for all the results of a specific type, for example? Or maybe i could add a "table_name" field on that arq_type table?

I think you're still referring to your original design here and not to the inheritance approach, right? In that case you probably want something like:

* sites
id_site
name
description
x
y
type_site text REFERENCES site_types

* site_types
type_site text PRIMARY KEY

If you use a natural key here (like I did above) you often don't even need to join with site_types, but it does give you a constraint what people can type in the field it relates to.
Note: I'm assuming that a site can only be of one type here, I didn't have enough information to go on so that may be wrong. It gets slightly more complicated if that's the case.

If you use table inheritance you'll have to redefine the foreign key constraint on each child table, as the FK constraint won't be inherited.

Alban Hertroys

--
If you can't see the forest for the trees,
cut the trees and you'll see there is no forest.

!DSPAM:737,4c376755286211334030252!

Miguel Vaz <pagongski@gmail.com> wrote:

Thank you for the opinion, Alban. The names are the least of my worries, i
typed them without thinking. And its portuguese. :-)

If, using that design, i had a different table with something like arq_types
{ id_arq_type, descr } that i could somehow connect to the generic table
(the one with the common fields), how could i go about querying those tables
for all the results of a specific type, for example? Or maybe i could add a
"table_name" field on that arq_type table?

Tim:

Dont consider this to be strictly for archeology, i mean in a generic sense
that if we have several data sets with common fields, if we could divide
them into several tables, one with common fields, and the others with fields
related to each type. My doubt was regarding how to have a separate table
with "types" that could be used to help query the "common fields table" and
fetch the corresponding table of that specific type. I understand its a bit
ungrateful for you guys to understand what i mean, considering that i am
probably making things even more confusing. :-)
[...]

I think the main problem is that you haven't stated your ex-
perience with SQL (or databases in general). Your questions
above ("somehow connect to the generic table", "go about
querying those tables") indicate that you seem to be lacking
basic knowledge. In this case, it won't help you, us or your
database to ask how to structure your data; you should read
a tutorial, and then choose a structure that you understand
and that works for you.

But at the moment, you're basically saying: "I'd like to
build a vehicle; I haven't decided yet whether it should
take me to the next pub or the moon. Which screws should I
use?"

Tim

Tim: ah, come on. :-P

I do have basic knowledge, and beyond. I am mostly a MySQL dev (dont flame
yet), but have a good grasp on bds in general.

I usually solve the BD problems/situations in a way i can easily code around
it, since i am normally the dev on the programming front also. This time i
am building the BD for someone else, with certain constraints, so my
question was more of a general use, or common procedure - if there is one -
for that particular problem.

I understand that you, Tim, might be more pragmatic about the whole matter,
and please forgive my use of english, which is also not my native language,
but its merely what i stated above: i do have knowledge, i can solve the
stated situation in a way *I* could work with, but thought of asking you,
master SQL'ers, about how you would solve the situation. Just that, no
strings attached, no complications needed. :-)

Email is a very ungrateful media for db explanations. It easily becomes
boring and extensive, for both the writer and the reader. Still, thanks for
the help, guys. :-)

As for the vehicle, Tim, i would prefer the pub, since at the moon is where
i usually spend my days, hehe.

Pag

On Fri, Jul 9, 2010 at 7:16 PM, Tim Landscheidt <tim@tim-landscheidt.de>wrote: