Thread: CHECK versus a Table for an enumeration

Hi all!

I want to know what's better between these 2 solutions :

CREATE TABLE user (
...
user_type   text     CHECK(user_type='Root' OR user_type = 'Admin' OR
user_type = 'Standard'));

or the following :

CREATE TABLE user_type(
user_type_id     integer   PRIMARY KEY,
user_type_desc text);

CREATE TABLE user (
...
user_type_id   integer,
CONSTRAINT user_type_exists FOREIGN KEY (user_type_id) REFERENCES
user(user_type_id));

I am really confused so I'll wait for your advices.

Thanks,

Melanie

On 22/12/2003 21:37 Melanie Bergeron wrote:
> Hi all!
>
> I want to know what's better between these 2 solutions :
>
> CREATE TABLE user (
> ...
> user_type   text     CHECK(user_type='Root' OR user_type = 'Admin' OR
> user_type = 'Standard'));
>
> or the following :
>
> CREATE TABLE user_type(
> user_type_id     integer   PRIMARY KEY,
> user_type_desc text);
>
> CREATE TABLE user (
> ...
> user_type_id   integer,
> CONSTRAINT user_type_exists FOREIGN KEY (user_type_id) REFERENCES
> user(user_type_id));
>
> I am really confused so I'll wait for your advices.
>
> Thanks,
>
> Melanie

just my personal opinion but here goes:

For the example you've provided I don't think theres much in it. The
second version would give you ability to change the text of the user type
if that were important and to add new user types without having to alter
constraints. So if I _had_ to choose, I'd take the second option.

HTH

--
Paul Thomas
+------------------------------+---------------------------------------------+
| Thomas Micro Systems Limited | Software Solutions for the Smaller
Business |
| Computer Consultants         |
http://www.thomas-micro-systems-ltd.co.uk   |
+------------------------------+---------------------------------------------+

On Mon, Dec 22, 2003 at 04:37:51PM -0500, Melanie Bergeron wrote:

> I want to know what's better between these 2 solutions :
>
> CREATE TABLE user (
> ...
> user_type   text     CHECK(user_type='Root' OR user_type = 'Admin' OR
> user_type = 'Standard'));
>
> or the following :
>
> CREATE TABLE user_type(
> user_type_id     integer   PRIMARY KEY,
> user_type_desc text);

Check out the second article at
                                        
http://www.varlena.com/varlena/GeneralBits/42.php

It contains some discussion on this issue.

--
Alvaro Herrera (<alvherre[a]dcc.uchile.cl>)
"The West won the world not by the superiority of its ideas or values
or religion but rather by its superiority in applying organized violence.
Westerners often forget this fact, non-Westerners never do."
(Samuel P. Huntington)

Hello Melanie

If your set of items will by static and small, then you can use CHECK
constraint. I use it for five, items itemes.

You can write more simple this constraint

...
user_type TEXT NOT NULL CHECK (user_type IN ('Root','Admin','Standard')),

regards
Pavel Stehule






On Mon, 22 Dec 2003, Melanie Bergeron wrote:

> Hi all!
>
> I want to know what's better between these 2 solutions :
>
> CREATE TABLE user (
> ...
> user_type   text     CHECK(user_type='Root' OR user_type = 'Admin' OR
> user_type = 'Standard'));
>
> or the following :
>
> CREATE TABLE user_type(
> user_type_id     integer   PRIMARY KEY,
> user_type_desc text);
>
> CREATE TABLE user (
> ...
> user_type_id   integer,
> CONSTRAINT user_type_exists FOREIGN KEY (user_type_id) REFERENCES
> user(user_type_id));
>
> I am really confused so I'll wait for your advices.
>
> Thanks,
>
> Melanie
>
>
> ---------------------------(end of broadcast)---------------------------
> TIP 5: Have you checked our extensive FAQ?
>
>                http://www.postgresql.org/docs/faqs/FAQ.html
>

On Mon, 22 Dec 2003, Melanie Bergeron wrote:

> Hi all!
>
> I want to know what's better between these 2 solutions :
>
> CREATE TABLE user (
> ...
> user_type   text     CHECK(user_type='Root' OR user_type = 'Admin' OR
> user_type = 'Standard'));

Will you ever in your wildest dreams need more or different values in
user_type?  If not them go here.  I user this for well known, limited
sets - Male/Female.

> or the following :
>
> CREATE TABLE user_type(
> user_type_id     integer   PRIMARY KEY,
> user_type_desc text);
>
> CREATE TABLE user (
> ...
> user_type_id   integer,
> CONSTRAINT user_type_exists FOREIGN KEY (user_type_id) REFERENCES
> user(user_type_id));
>
> I am really confused so I'll wait for your advices.

This when there is a chance, any chance, you'll need to add to the list or
make changes to user_type_desc.


Rod
--
    "Open Source Software - You usually get more than you pay for..."
     "Build A Brighter Lamp :: Linux Apache {middleware} PostgreSQL"

Thank you very much to you all. I'll choose the second option to be more
flexible.

Melanie