Domains in Ingres

[koyott]

Hello colleagues!
Please tell me how can I use domains in Ingres sql?
As I know "Create domain" is a standart Transact-SQL operator, but there is nothing about that in Ingres SQL reference guide! Is there any analog?

[stephenb]

I'm guessing you are talking about the ANSI standard schemas (TSQL probably calls them domains). Ingres supports schemas only in a basic fashion; in Ingres a shcema name is the same as your user name, you can only create tables in the schema that is your current user name (which may be modified either with "-u" flag or wit SET SESSION AUTHORIZATION). created tables may be refference by their schema (e.g. select * from <schema_name>.<table_name>)

[koyott]

I'm talking about how can I control values of attributes in table:
One of control methods is check constraints; other method is to create "domain" for an attribute to check if input values are (or not) agree with that domain. May be I'm confused with an idea?

[kschendel]

Ingres does not support domains in the sense of T-SQL. They would essentially translate to a check constraint anyway, so in Ingres, use a check constraint.

[stephenb]

Yup, Karl pretty much summed it up....domains are a TSQL specific concept that doesn't exist in other databases, you should use a check constraint instead.

[rhann]

Originally Posted by stephenb

Yup, Karl pretty much summed it up....domains are a TSQL specific concept that doesn't exist in other databases, you should use a check constraint instead.

That is not correct. CREATE DOMAIN and ALTER DOMAIN are both part of standard SQL92. Furthermore, inadequate though the SQL concept of domain is, it still does very much more than a check constraint on an individual column because it harmonizes representations between tables (preventing function attribute joins and other undesirable goofs).

I would very much welcome domain support in Ingres.

I'll get back into my box now. I feel grubby using these [blessed] web-based forums...

[stephenb]

well I'll be....never noticed that before, it's a good job I'm not on the ANSI committee.

It's the first time someone has mentioned this particular ANSI feature to my knowledge; I wonder how prevalent it is in SQL Server installations. Presumably Oracle has it too.

[koyott]

This is interest to me:
If domains are in SQL92 standart (really, I've just checked), and my Ingres installation supports that standart (option during installation), that's why Ingres must support this SQL92 statement (Create/Alter domain)
But as I see it doesn't??!!

see here:
http://www.ncb.ernet.in/education/mo...075-1-1999.pdf
http://www.iso.org/iso/iso_catalogue...csnumber=16663

[kschendel]

Ingres is technically compliant to the "Entry Level" SQL-92 spec only. I don't have the SQL-92 spec in front of me (thank goodness!!!), but I doubt that domains are Entry Level.

I don't mean to blow you off, but domains as they exist in SQL (as far as I know) are a quite limited construct. They are equivalent to a globally defined CHECK constraint, and add little or no value to most business logic constraints. I suppose it would be nice if Ingres supported domains, but it has to be not real high up on the list of things to do to Ingres.

[stephenb]

There are several SQL-92 and SQL3 extensions that Ingres doesn't support; I don't think anyone supports everything, with the possible exception of Oracle.

Since this is the first time we're hearing about this particular one, as Karl says, it's not that high on a very long "to-do" list.....of course if anyone would like to code it, we'll be more than happy to accept it back into the code base.