Hello Gordon,
> And now we are down to reality. This is a MySQL list. Views are a
wonderful
> thing for creating an isolation layer between the application and the
> database. However, MySQL's current implementation makes it extremely
> difficult in many cases to avoid full table scans when you de
f
Database magazine. In the end I believe they agreed to disagree.
-Original Message-
From: Martijn Tonies [mailto:[EMAIL PROTECTED]
Sent: Thursday, March 16, 2006 5:33 AM
To: mysql@lists.mysql.com
Subject: Re: Accountability with MySQL
From: <[EMAIL PROTECTED]>
> "Martijn T
> >> > Read the literature on how to design databases. What you do
> >> > is storing "true propositions". That is, each attribute defines a
> >> > certain "true proposition". For example:
> >> >
> >> > Employee "Martijn" has Employee# 14.
> >> >
> >> > You should be able to derive these sentences f
James,
> Also, surely if you left join to a table then if there's no matching row
you get a null value in your result set. So I'm not sure what the difference
is between getting that null because you store it in a column in the primary
table, and deriving it by left joining to a related table wit
Also, surely if you left join to a table then if there's no matching row you
get a null value in your result set. So I'm not sure what the difference is
between getting that null because you store it in a column in the primary
table, and deriving it by left joining to a related table with no mat
> > > in order to retrieve all the information about them. Replacing a
> > > theoretically ugly null flag with a 10 way join strikes me, as an
> engineer
> > > rather than a theoretician, the wrong side of the
> elegance/practicality
> > > trade-off.
> >
> > Using NULLs as well as de-normalization
"Martijn Tonies" <[EMAIL PROTECTED]> wrote on 16/03/2006 11:32:45:
> From: <[EMAIL PROTECTED]>
> > "Martijn Tonies" <[EMAIL PROTECTED]> wrote on 16/03/2006 11:02:32:
> >
> > > Well, the question still is if you should store "unknown" at all ;)
> > >
> > > Not according to Date: you should store wh
From: <[EMAIL PROTECTED]>
> "Martijn Tonies" <[EMAIL PROTECTED]> wrote on 16/03/2006 11:02:32:
>
> > Well, the question still is if you should store "unknown" at all ;)
> >
> > Not according to Date: you should store what is known. See the remarks
> > about the "true propositions", from which relat
> > Ah well, SQL (these days) provides plenty of functions to avoid
> > the problems. Coalesce being one of them...
> >
> > How often do people write:
> >
> > (probably not valid MySQL)
> > select firstname || coalesce(middlename || ' ', ' ') || lastname
> > from ...
> >
> Your syntax isn't quite
"Martijn Tonies" <[EMAIL PROTECTED]> wrote on 16/03/2006 11:02:32:
> Well, the question still is if you should store "unknown" at all ;)
>
> Not according to Date: you should store what is known. See the remarks
> about the "true propositions", from which relational databases are
derived
> (but
> But (in at least some situations) is not appropriate to record that you
know that you don't have a value?
>
Sure it would. It it's needed.
But the answer doesn't have to be a NULL. Remember
the example about recording the fact that a student did
not make a test for whatever reason?
It was th
But (in at least some situations) is not appropriate to record that you know
that you don't have a value?
I think the words of Donald Rumsfeld are appropriate here:
"There are known knowns. These are things we know that we know. There are known
unknowns. That is to say, there are things that we
From: "Mark Leith"
> Martijn Tonies wrote:
>
> >We're arguing about whether or not your database design
> >(as stored on disk) should contain NULLs.
> >
> >IMO: no, or at least as few as possible.
> >
> >
> I believe the answer really is - *it depends*.
>
> You are both right, really. Martijn,
Martijn Tonies wrote:
We're arguing about whether or not your database design
(as stored on disk) should contain NULLs.
IMO: no, or at least as few as possible.
I believe the answer really is - *it depends*.
You are both right, really. Martijn, yes, according to academia and
proper databa
From: "James Harvard"
> At 7:28 pm +0100 14/3/06, Martijn Tonies wrote:
> >Given that NULLs basically means the absence of a value (eg: unknown),
you shouldn't be storing NULLs.
>
> At 1:49 pm -0500 14/3/06, Rhino wrote:
> >A null means "unknown or not applicable" and is a perfectly valid value
to
At 7:28 pm +0100 14/3/06, Martijn Tonies wrote:
>Given that NULLs basically means the absence of a value (eg: unknown), you
>shouldn't be storing NULLs.
At 1:49 pm -0500 14/3/06, Rhino wrote:
>A null means "unknown or not applicable" and is a perfectly valid value to use
>in many, many situation
A commonly used example (at least at my last 3 jobs) would be a table of
demographics for people (whether they be employees, clients, whatever).
You can have one table and allow NULLs for some of the fields (id,
LastName, FirstName, MiddleInitial, Title, NameSuffix, AddressLine1,
AddressLine2,
- Original Message -
From: "Martijn Tonies" <[EMAIL PROTECTED]>
To:
Sent: Wednesday, March 15, 2006 10:47 AM
Subject: Re: Accountability with MySQL
Hello,
(please read all before replying)
>> >> > Basics of database design: store what you know.
&
Hello,
(please read all before replying)
> >> >> > Basics of database design: store what you know.
> >> >> >
> >> >> > Given that NULLs basically means the absence of a value
> >> >> > (eg: unknown), you shouldn't be storing NULLs.
> >> >> >
> >> >> Nonsense!!
> >> >
> >> > That's a bold statemen
- Original Message -
From: "Martijn Tonies" <[EMAIL PROTECTED]>
To:
Sent: Wednesday, March 15, 2006 2:53 AM
Subject: Re: Accountability with MySQL
>> > Basics of database design: store what you know.
>> >
>> > Given that NULLs basi
> >> > Basics of database design: store what you know.
> >> >
> >> > Given that NULLs basically means the absence of a value
> >> > (eg: unknown), you shouldn't be storing NULLs.
> >> >
> >> Nonsense!!
> >
> > That's a bold statement ...
> >
> >> That's simply wrong. A null means "unknown or not ap
> At 7:48 pm -0500 14/3/06, Rhino wrote:
> >>Ah, so now things become clear, a NULL actually can mean
> >>two things? So much for clarity then...
> >
> >Come on; that's not fair. "Unknown" and "not applicable" are more like
different senses of the same thing, not two opposite things.
>
>
> IIRC (
At 7:48 pm -0500 14/3/06, Rhino wrote:
>>Ah, so now things become clear, a NULL actually can mean
>>two things? So much for clarity then...
>
>Come on; that's not fair. "Unknown" and "not applicable" are more like
>different senses of the same thing, not two opposite things.
IIRC (but please don'
- Original Message -
From: "Martijn Tonies" <[EMAIL PROTECTED]>
To: "Rhino" <[EMAIL PROTECTED]>;
Sent: Tuesday, March 14, 2006 2:16 PM
Subject: Re: Accountability with MySQL
> >Should you have a flag for the status "movement complet
- Original Message -
From: "Bruno B B Magalháes" <[EMAIL PROTECTED]>
To:
Sent: Tuesday, March 14, 2006 2:07 PM
Subject: Re: Accountability with MySQL
I am designing a simple accountability system so all the partners can
have
direct access to it by intranet.
I w
> > >Should you have a flag for the status "movement complete" ? I would say
> >>yes but instead of a simple checkbox, you could store a date value. That
> >>gives you two pieces of information
> >>
> >>a) if the date is null then the movement is not complete.
> >>b) if the date is NOT null then t
>>I am designing a simple accountability system so all the partners can
>> have
>> direct access to it by intranet.
>>
>> I was designing the data model, and came up with this:
>>
>> CREATE TABLE `moviments` (
>> `moviment_id` int(20) NOT NULL auto_increment,
>> `moviment_date` date NOT NULL def
- Original Message -
From: "Martijn Tonies" <[EMAIL PROTECTED]>
To:
Sent: Tuesday, March 14, 2006 1:28 PM
Subject: Re: Accountability with MySQL
>Should you have a flag for the status "movement complete" ? I would say
yes but instead of a simple che
- Original Message -
From: "Martijn Tonies" <[EMAIL PROTECTED]>
To:
Sent: Tuesday, March 14, 2006 1:16 PM
Subject: Re: Accountability with MySQL
Hello Bruno,
well about the date default value being invalid, well it´s working here
in
my system (MySQL 4.1.16, Mac O
Hello Shawn,
> > well about the date default value being invalid, well it´s working here
in
> > my system (MySQL 4.1.16, Mac OS X 10.4.5), and all my systens work with
> > this...
>
> Yes, it's a valid value in MySQL, but it's an invalid date,
> that's what I'm trying to say. Why have an invalid d
- Original Message -
From: "Bruno B B Magalháes" <[EMAIL PROTECTED]>
To:
Sent: Tuesday, March 14, 2006 12:41 PM
Subject: Accountability with MySQL
I am designing a simple accountability system so all the partners can have
direct access to it by intranet.
I was de
>Should you have a flag for the status "movement complete" ? I would say
>yes but instead of a simple checkbox, you could store a date value. That
>gives you two pieces of information
>
>a) if the date is null then the movement is not complete.
>b) if the date is NOT null then the movement is compl
"Martijn Tonies" <[EMAIL PROTECTED]> wrote on 03/14/2006 01:16:11 PM:
> Hello Bruno,
>
> > well about the date default value being invalid, well it´s working
here in
> > my system (MySQL 4.1.16, Mac OS X 10.4.5), and all my systens work
with
> > this...
>
> Yes, it's a valid value in MySQL, bu
Hello Bruno,
> well about the date default value being invalid, well it´s working here in
> my system (MySQL 4.1.16, Mac OS X 10.4.5), and all my systens work with
> this...
Yes, it's a valid value in MySQL, but it's an invalid date,
that's what I'm trying to say. Why have an invalid date
as the
Bruno B B Magalháes <[EMAIL PROTECTED]> wrote on 03/14/2006 12:41:35
PM:
> I am designing a simple accountability system so all the partners can
have
> direct access to it by intranet.
>
> I was designing the data model, and came up with this:
>
> CREATE TABLE `moviments` (
> `moviment_id` i
Hi Martijn,
well about the date default value being invalid, well it´s working here in
my system (MySQL 4.1.16, Mac OS X 10.4.5), and all my systens work with
this...
About the business logic I was thinking about showing the current month by
default, and if the user wants he can select diferent d
Hello Bruno,
> I am designing a simple accountability system so all the partners can have
> direct access to it by intranet.
>
> I was designing the data model, and came up with this:
>
> CREATE TABLE `moviments` (
> `moviment_id` int(20) NOT NULL auto_increment,
> `moviment_date` date NOT NUL
I am designing a simple accountability system so all the partners can have
direct access to it by intranet.
I was designing the data model, and came up with this:
CREATE TABLE `moviments` (
`moviment_id` int(20) NOT NULL auto_increment,
`moviment_date` date NOT NULL default '-00-00',
`m
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