Just a little remark: the createDatabase.rex example uses in its
create-statements "not null", but
supplies default values being empty strings.
>From a database conceptual view this is illogical: NULL represents the missing
>of information and
obviously the empty string represents missing information as well. The problem
however: one cannot
distinguish anymore between an empty string that the user supplied from a
missing value (the user
has not supplied any value) anymore!
So the suggestion would be to leave out the default '' part to re-enable the
ability to find those
records in which values are truly missing, i.e. are NULL. Only use NOT NULL for
columns that must
have a value under all conditions (i.e. for all candidate primary keys).
---
As your tables possess foreign key relationships to the "contacts" table, it
might be helpful to
define foreign key relationships from the tables "addresses" and
"TABLE_phone_num" to the table
"contacts", cf. <http://www.sqlite.org/foreignkeys.html>. Probably something
like (untested):
...
CREATE TABLE addresses (
...
, *FOREIGN KEY(contact_id) REFERENCES contacts(id) ON UPDATE CASCADE ON
DELETE CASCADE
*, *FOREIGN KEY(type_id) REFERENCES addr_type(addr_type_id) ON UPDATE
CASCADE ON DELETE RESTRICT*
);*
*CREATE TABLE TABLE_phone_num (
...
, *FOREIGN KEY(contact_id) REFERENCES contacts(id) **ON DELETE CASCADE*
);
In the above table there is a column "type_id": what kind of a type id is this?
Does the value (if
given) refer to an existing value in another table (being a foreign key then)?
Or is this line just
a copy & paste oversight?
CREATE TABLE inet_addr (
...
, *FOREIGN KEY(contact_id) REFERENCES contacts(id) **ON DELETE CASCADE*
* *, *FOREIGN KEY(type_id) REFERENCES addr_type(addr_type_id) ON UPDATE
CASCADE ON DELETE RESTRICT*
);
...
Please keep up your excellent work!
---rony
P.S.: Many years ago (actually about twenty years ago) I held lectures on
relational databases
(Oracle, DB2, SQLServer) and wrote even a little book on designing relational
models and introducing
SQL. The NULL concept turned out to be one that needed special attention, hence
this preliminary
feedback. (Sorry, have not been able to run the samples and study the classes
and APIs yet.)
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