[Tutor] Database topic now fixed

[Alan Gauld]

Thanks Bob,

Feedback is always appreciated, its how the tutor improves.

> 1 - people familiar with other databases might be puzzled by the 
> lack of column datatypes. I'd mention that sqlite allows but does 
> not require types at the first introduction of CREATE TABLE,.

Fair point, although by definition my tutor is aimed at absolute
novices so they are less likely to know about SQL. But I will
make a comment.

> 2 - The introduction of NULL: "NOT NULL is self explanatory, it 
> indicates that the value must exist and not be NULL."

Oops, self referencing definitions are never good (unless its GNU)
I'll fix that one.

> > 3 - "UNIQUE means that the value must be unique within the table. 
> > If it
> slightly confusing (and not totally true "unique within the table" 
> really is within the column).

Quite right, I'll clarify it.

> 4 - introducing WHERE. I'd first show it as WHERE x = y and then 
> introduce the table prefix.

My general style in the tutor is to teach the most general case first
then introduce the shortcuts. Fully specified names will never go
wrong but shortened names can cause confusion in my experience.
So for this one I'lll stick with the long way first then introduce
the shoirter form.

> 5 - following the explanation of UNIQUE under constraints, please 
> also explain DEFAULT.

Fair point.

> 6- the table structure in Address Book Revised looks like it is for 
> UK addresses. Consider saying this. Also consider a structure that 
> would accommodate US/Canadian address also.

Erm, What is the difference exactly?

> 7 - "SELECT First,Last, Phone FROM Address WHERE First Like Dav%;" 
> Shouldn't Dav% be in quotes?

Oops yes, it is in my actual code but they have been dropped in the
editing somewhere.

Oh well, not quite as faultless as I hoped but better than it was! :-)

Thanks for the feedback Bob, I'll incorporate most of it in the next
upload.

Alan Gauld
Author of the Learn to Program web site
http://www.freenetpages.co.uk/hp/alan.gauld