Re: codd's 12 Rules

Actually, from what I've read, being able to use languages outside of SQL
to access the database is not a violation. As long as said access will
not allow you to work around the restrictions imposed on it. For example,
if you have a check constraint that only allows '0' or '1' for the active
record code and your RLA access does not allow you to get by that, then
the RLA is not in violation.

The argument against DDS is probably because it's CHECK keyword is not a
valid check constraint. That's easy to get around. If you enhance DDS
with ADDPFCST that's different. If you want to store alphabetic data in a
numeric column in a DDS defined table, no problem, can do. With a DDL
defined table, that's not going to happen. And this is where DDS defined
tables fail Codd's rules. Take this decimal column, AccountBalance. Now
use it in RPG with this (column positions not exact)
D DS
D AccountBalance 9P 2
D CountryCode 5A overlay(AccountBalance)
read ddstable;
CountryCode='USA ';
update ddstable;

Or, an even simpler example with no programming involved, create a table
with DDS with numeric columns. Figure out the record length. Create a
new table with that same record length without DDS or SQL; CRTPF ...
RCDLEN(##). Insert one row into the latter table of all alphabetic
characters. Use CPYF to copy over the DDS defined table and you have
characters in numeric data. A DDL table will reject the CPYF.



Rob Berendt