[Gambas-user] [slightly OT] No Problem with Gambas or MySql!

[Willy Raets]

On Sun, 2013-10-06 at 00:05 +0200, Caveat wrote:
> > If you wanted to delete one row with values 347 200, then which row would it be?
> 
> It *doesn't matter*!  The rows are the same, so pick a row, ANY row!

That is exactly what I have been doing for the last 10 years.
In VB code I just looked for the criteria in the table and deleted the
first record that met the criteria, next update table and ready.

In Gambas I tried the same, now with the table being in MySql, and it
didn't work.

It never, ever failed me in those 10 years, even without a primary key.
Although most other tables do have primary keys and relations set up,
there never was a need for this table to have a primary key.
And I still do not see the need for a primary key.

> 
> > Without the primary key, you're asking MySQL to guess, and it wont.
> 
> Yes it will, if you use LIMIT (see my previous two mails).  Otherwise, it'll happily delete all the rows that meet the criteria, whether they're duplicates or not.
> 

And even in MySql there is NO need for the table to have a primary key
as the 'SELECT ... limit 1' will do what I expect, delete only 1 record
that meets the criteria.

> > >"duplicate rows are and always were a mistake in SQL", C.J.Date

Duplicate rows are a reality in real life data gathering.
I have been working with databases since dbase somewhere in the '80's
and I have had to deal with real life situations concerning data
storage, not with theory for ideal models. Not saying I haven't read my
share on relational database design and take it into account when
designing a database.

> 
> The guy has obviously never read William Kent's "Data and Reality". It's 
> a book I'd still recommend to anyone working with data and particularly 
> databases, even though it was written 35 years ago!
> 
> <RANT>
> Why *must* every record be uniquely identifiable?  Explain why... don't 
> just throw random snippets of relational database theory at me!  If I 
> ask you to model the contents of your pockets on a database, are you 
> going to attach some artificial key to each individual penny?  Why?  
> They each buy the same number of penny chews (showing my age!), and if 
> you take 3 pennies away, you've still got 3 pennies less than you had 
> before, no matter how carefully you select those 3 pennies!
> </RANT>
> 
> <HINT>
> A tuple is, by definition, unique.  If I have 8 rows on my database 
> representing 8 real-world penny objects and I can delete 3 of them... 
> are the remaining 5 rows tuples?  How closely does the database model 
> reality in this case?
> </HINT>

I like your penny story ;)


-- 
Kind regards,

Willy (aka gbWilly)

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