Re: Avoiding New Fields Causing Ambiguity Errors
Date: 13 May 2002 10:13:28 -0700
lennart_at_kommunicera.umea.se (Lennart Jonsson) wrote in message news:<6dae7e65.0205071347.1b3022d2_at_posting.google.com>...
> topmind_at_technologist.com (Topmind) wrote in message news:<4e705869.0205071035.14dc571a_at_posting.google.com>...
> > Title: Avoiding New Fields Causing Ambiguity Errors
> > There is the possibility when adding a new field that an existing
> > query(s) in an application(s) might "break" due to field name
> > ambiguity being introduced. Other than relying on regression testing,
> > approaches to avoid or reduce this include:
> > 1. Have a systematic way to check for fields with the same name(s) as
> > the candidate field(s) already in the schema somewhere. This may lead
> > to names like "X_status" and "X_title" instead of "status" and "title"
> > where "X" is the table name. (This practice makes queries simpler in
> > many cases anyhow.)
> > 2. Have the query engine *ignore* duplicates by picking the oldest
> > table and/or fields, or even have ranks assigned to tables or fields
> > in case there is a conflict. This is probably not a perfect solution,
> > but may reduce the chances of behavior change. (Of course, this should
> > be an optional switch.)
> > 3. Toss SQL in favor of other relational query languages. (Not likely
> > to happen any time soon, but I thought I would include it for the heck
> > of it.)
> > Is there any "best practices" standards that deal with this issue?
> Best I can think of is to always qualify tabls and columns as in:
> select c.name, d.name from myscheme.cars c, myscheme.drivers d ...
It seems that some database engines don't let one use
alias columns within WHERE clauses for some odd
reason. I often get "invalid column" when I try to do
this. Thus, I have to resort to the "native" name
with a table/entity qualifier in WHERE clauses.
This works, but makes generated
criteria code more difficult to manage because the result set column name differs from the criteria column name.
> just my 3 skr thoughts
> > Thanks, -T.O.P.head-
Thanks for your feedback,
-T- Received on Mon May 13 2002 - 19:13:28 CEST