Re: Foreign key in Oracle Sql

From: DA Morgan <damorgan_at_x.washington.edu>
Date: Fri, 14 Jan 2005 20:17:49 -0800
Message-ID: <41e89962$1_1@127.0.0.1>

ak_tiredofspam_at_yahoo.com wrote:

>>>What do you mean there is no VARCHAR2? Are you saying there are no

>
> variable length strings in SQL?
> ..<<
>
> it's called VARCHAR

In a specific product. Does that mean that other products should rename their features?

SQL*Plus: Release 10.1.0.3.0 - Production on Fri Jan 14 20:12:13 2005

Connected to:
Oracle Database 10g Enterprise Edition Release 10.1.0.3.0 - Production With the Partitioning, OLAP and Data Mining options

SQL> CREATE TABLE dense (

2 varchar2col VARCHAR2(20),
3 varchar_col VARCHAR(20));

Table created.

SQL> desc dense

  Name                                      Null?    Type
  ----------------------------------------- -------- ------------------
  VARCHAR2COL                                        VARCHAR2(20)
  VARCHAR_COL                                        VARCHAR2(20)

SQL> In Oracle VARCHAR exists. But because it is part of the C language it is usable in that context. Perhaps your product doesn't have an equivalent to Pro*C ... or a history that goes back before Microsoft.

>>> Are you saying NULLS should propagate

>
> as strings?
> ..<<
>
> Well, I don't have a middle name, which is a very different situation
> from unknown middle name, correct? So I fail to see the logic in
> Oracle's inability to distinguish between a known empty string and an
> unknown one
>
> SELECT COALESCE('', 'Null') FROM DUAL;
> ---------------
> Null
>
> What do you think?

I think NULL means a lack of a value .... I think a zero length string is a zero length string from twoentirely different things. BTW ... NULL in Oracle does not have single quotes around it.

And I think the entire posturing is a bit ridiculous as each vendors does what they want and those that use their products adjust to their strengths and weaknesses. If you don't like a product ... don't use it. That one calls it VARCHAR, another VARCHAR2, and another PURPLERHINO has a zero value proposition.

-- 
Daniel A. Morgan
University of Washington
damorgan_at_x.washington.edu
(replace 'x' with 'u' to respond)

Received on Fri Jan 14 2005 - 22:17:49 CST