Обсуждение: Link many attributes in one table to one attribute in another??

Hello all,

I am fairly new at db design, I have built a few simple in the past and have
never dealt with this type of problem before, any help would be appreciated.

I have three attributes in one table that should reference one, and only
one, attribute in another table. Here's an analogy of the problem:

I have a table with a list of marbles, each marble has three colors in it
(color1, color2, color3) and a serial number. In another table I have eight
colors to choose from but the list of colors grows regularly.
How do I associate a marble with three colors from the color table (a marble
may have three red sides or red-yellow-blue)?

Thanks,
Christian

A easy way to handle this:

create table marble
(   id     int4 primary key,   color1 int4,   color2 int4,   color3 int4
);

create table color
(   id     int4,   desc   text
);

color1, color2, and color3 point to the id in color table.

This way you can expand your color table indefinitely.

On 27 Jun 2001 23:44:34 -0500, Christian Anton wrote:
> Hello all,
> 
> I am fairly new at db design, I have built a few simple in the past and have
> never dealt with this type of problem before, any help would be appreciated.
> 
> I have three attributes in one table that should reference one, and only
> one, attribute in another table. Here's an analogy of the problem:
> 
> I have a table with a list of marbles, each marble has three colors in it
> (color1, color2, color3) and a serial number. In another table I have eight
> colors to choose from but the list of colors grows regularly.
> How do I associate a marble with three colors from the color table (a marble
> may have three red sides or red-yellow-blue)?
> 
> Thanks,
> Christian
> 
> 
> 
> ---------------------------(end of broadcast)---------------------------
> TIP 6: Have you searched our list archives?
> 
> http://www.postgresql.org/search.mpl
> 

-- 
Wei Weng
Network Software Engineer
KenCast Inc.

"Christian Anton" <christiananton@hotmail.com> wrote in message
news:3b3ab3aa_1@newsa.ev1.net...

> I have a table with a list of marbles, each marble has three colors in it
> (color1, color2, color3) and a serial number. In another table I have
eight
> colors to choose from but the list of colors grows regularly.
> How do I associate a marble with three colors from the color table (a
marble
> may have three red sides or red-yellow-blue)?

Not sure what you mean exactly, but the following:

CREATE TABLE marbles ( m_id   serial, m_col1 int4, m_col2 int4, m_col3 int4
);

CREATE TABLE colours ( c_id   serial, c_name text
);

INSERT INTO colours (c_name) VALUES ('red');
INSERT INTO colours (c_name) VALUES ('green');
INSERT INTO colours (c_name) VALUES ('blue');
INSERT INTO marbles (m_col1,m_col2,m_col3) VALUES (1,1,1);
INSERT INTO marbles (m_col1,m_col2,m_col3) VALUES (1,2,3);
INSERT INTO marbles (m_col1,m_col2,m_col3) VALUES (3,2,1);

SELECT m.m_id, c1.c_name as colname1, c2.c_name as colname2, c3.c_name as
colname3
FROM marbles m
JOIN colours c1 ON m.m_col1 = c1.c_id
JOIN colours c2 ON m.m_col2 = c2.c_id
JOIN colours c3 ON m.m_col3 = c3.c_id;


Will produce:
m_id | colname1 | colname2 | colname3
------+----------+----------+----------   1 | red      | red      | red   3 | blue     | green    | red   2 | red
|green    | blue
 


We join the colours table to the marbles table three times and need to alias
it differently each time. Otherwise, we don't know which colour-name matches
which colour-code.

If it's not that simple, can we have table definitions and an example of the
sort of output you'd like?

- Richard Huxton

On Thursday, 28. June 2001 06:44, Christian Anton wrote:
> Hello all,
>
> I am fairly new at db design, I have built a few simple in the past
> and have never dealt with this type of problem before, any help would
> be appreciated.
>
> I have three attributes in one table that should reference one, and
> only one, attribute in another table. Here's an analogy of the
> problem:
>
> I have a table with a list of marbles, each marble has three colors
> in it (color1, color2, color3) and a serial number. In another table
> I have eight colors to choose from but the list of colors grows
> regularly. How do I associate a marble with three colors from the
> color table (a marble may have three red sides or red-yellow-blue)?

Quite easy:

-- The list of colors. id is a automatically assigned unique number.
-- You could use INT4 instead of SERIAL and make numbers of your own.
CREATE TABLE color (id    SERIAL    PRIMARY KEY,name    text
);

-- The list of marbles. The colors reference to the table color.
-- Postgres makes sure that only existing colors are entered.
CREATE TABLE marble (number    SERIAL    PRIMARY KEY,color1    int4    REFERENCES color,color2    int4    REFERENCES
color,color3   int4    REFERENCES color
 
);

-- But you want to see the color's name rather its id, isn't it?
CREATE VIEW v_marble ASSELECT m.number, c1.name as color1, c2.name as color2, c3.name as color3FROM marble m, color c1,
colorc2, color c3WHERE m.color1 = c1.id  AND m.color2 = c2.id  AND m.color3 = c3.id;
 

Hope that helps.
Christof
--          gl.aser . software engineering . internet service      http://gl.aser.de/  . Planckstraße 7 . D-39104
Magdeburg
Tel. +49.391.7 44 77 10 . Fax +49.391.7 44 77 13 . Mobil 0177.77 92 84 3