Re: RE: RE: Data Modeling
Thanks for the information. The thumb rule and all will definitely help me in modelling. Thanks a Lot Best Regards B S Pradhan On Wed, 22 Oct 2003 Michael Milligan wrote : >Hi Again, > >What I do when a model is going to change is try to make it as flexible as >possible from the start. Build more abstraction into the model than you >normally would. Normalization is even more important here, even going to 4th >or 5th form, or at least Boyce-Codd 3rd. You want to design it so that when >someone wants to change the structure, it may be facilitated by the addition >of a new record instead of a new column. A very simplistic example would be >to have a separate address entity allowing for the possibility of multiple >addresses per customer, instead of building the address attributes right >into the customer entity. A good rule of thumb: whatever will change should >be changeable by addition or subtraction of a row. Whatever won't change is >a candidate for a column. That's a generalization, but a good rule >nonetheless. > >Data Architect from Sybase, ER/Studio from Embarcadero, Erwin from Computer >Associates are all good tools and easy to learn. QDesigner is the Data >Architect physical modeler repackaged by Quest and sold for less. Excellent >tool. > >Michael > > >This e-mail, including attachments, may include confidential and/or >proprietary information, and may be used only by the person or entity to >which it is addressed. If the reader of this e-mail is not the intended >recipient or his or her authorized agent, the reader is hereby notified that >any dissemination, distribution or copying of this e-mail is prohibited. If >you have received this e-mail in error, please notify the sender by replying >to this message and delete this e-mail immediately. >-- >Please see the official ORACLE-L FAQ: http://www.orafaq.net >-- >Author: Michael Milligan > INET: [EMAIL PROTECTED] > >Fat City Network Services-- 858-538-5051 http://www.fatcity.com >San Diego, California-- Mailing list and web hosting services >- >To REMOVE yourself from this mailing list, send an E-Mail message >to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in >the message BODY, include a line containing: UNSUB ORACLE-L >(or the name of mailing list you want to be removed from). You may >also send the HELP command for other information (like subscribing).
RE: RE: Data Modeling
Hi Again, What I do when a model is going to change is try to make it as flexible as possible from the start. Build more abstraction into the model than you normally would. Normalization is even more important here, even going to 4th or 5th form, or at least Boyce-Codd 3rd. You want to design it so that when someone wants to change the structure, it may be facilitated by the addition of a new record instead of a new column. A very simplistic example would be to have a separate address entity allowing for the possibility of multiple addresses per customer, instead of building the address attributes right into the customer entity. A good rule of thumb: whatever will change should be changeable by addition or subtraction of a row. Whatever won't change is a candidate for a column. That's a generalization, but a good rule nonetheless. Data Architect from Sybase, ER/Studio from Embarcadero, Erwin from Computer Associates are all good tools and easy to learn. QDesigner is the Data Architect physical modeler repackaged by Quest and sold for less. Excellent tool. Michael This e-mail, including attachments, may include confidential and/or proprietary information, and may be used only by the person or entity to which it is addressed. If the reader of this e-mail is not the intended recipient or his or her authorized agent, the reader is hereby notified that any dissemination, distribution or copying of this e-mail is prohibited. If you have received this e-mail in error, please notify the sender by replying to this message and delete this e-mail immediately. -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Michael Milligan INET: [EMAIL PROTECTED] Fat City Network Services-- 858-538-5051 http://www.fatcity.com San Diego, California-- Mailing list and web hosting services - To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
RE: RE: Data Modeling
Hi Again, What I do when a model is going to change is try to make it as flexible as possible from the start. Build more abstraction into the model than you normally would. Normalization is even more important here, even going to 4th or 5th form, or at least Boyce-Codd 3rd. You want to design it so that when someone wants to change the structure, it may be facilitated by the addition of a new record instead of a new column. A very simplistic example would be to have a separate address entity allowing for the possibility of multiple addresses per customer, instead of building the address attributes right into the customer entity. A good rule of thumb: whatever will change should be changeable by addition or subtraction of a row. Whatever won't change is a candidate for a column. That's a generalization, but a good rule nonetheless. Data Architect from Sybase, ER/Studio from Embarcadero, Erwin from Computer Associates are all good tools and easy to learn. QDesigner is the Data Architect physical modeler repackaged by Quest and sold for less. Excellent tool. Michael This e-mail, including attachments, may include confidential and/or proprietary information, and may be used only by the person or entity to which it is addressed. If the reader of this e-mail is not the intended recipient or his or her authorized agent, the reader is hereby notified that any dissemination, distribution or copying of this e-mail is prohibited. If you have received this e-mail in error, please notify the sender by replying to this message and delete this e-mail immediately. -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Michael Milligan INET: [EMAIL PROTECTED] Fat City Network Services-- 858-538-5051 http://www.fatcity.com San Diego, California-- Mailing list and web hosting services - To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
Re: RE: Data Modeling
Hey Michael I enjoyed your write-up.. especially a few db guys telling 'its relational because they are related'... I have also heard about it and the fact is that SQL the language for all the RDBMA is based on relational algebra and relational calcus and there in maths a rwo-column structure is called a relation. During my acadamics I have studied the book by Korth and Sudarshan and i know er-diagram and normalization theoritically. My major experience is with production dbs (where the schema structure hardly changes) and the new assignment mostly involves data modelling.. and that too the model will not be freezed soon. it will change very frequently for quite sometime. Was wondering how can i manage db table/proc structure changes from different sectors and integrate them at the end of the day. I donot know erwin or designer etc. Thanks a lot Regards B S Pradhan -- On Tue, 21 Oct 2003 Michael Milligan wrote : >I would read some of C.J. Date's papers, or books from his "Relational >Database Writings" series. Also, there is a recent book called "Data >Modeling for Everyone" by Sharon Allen (Curlingstone Press) which is good. > >Most importantly, understand the fundamental principles of relational theory >as it pertains to relational databases. If you make an effort at this >you'll be ahead of 90% of developers/DBAs in this area, in my opinion. I've >heard "database experts" say that relational databases are called that >because they "relate" one table to another. This is false. It is called >"relational" because it is based on relational math, and because columns are >grouped together into special relations called relational tables. We call >them tables for short. > >The important thing to note here is this: the relationship that matters most >is the relationship among the columns of the SAME TABLE. That they really do >belong together is the most important thing to be sure of in data modeling. >They need to be "functionally dependent" on the same set of primary key >columns. Functional dependency is hugely important to understand and is the >basis of good data modeling. > >Some authors: > >C.J. Date >Fabian Pascal >Sharon Allen > >many others as well. > >HTH, > >Michael Milligan >Oracle DBA >Ingenix, Inc. >2525 Lake Park Blvd. >Salt Lake City, Utah 84120 >wrk 801-982-3081 >mbl 801-628-6058 >[EMAIL PROTECTED] > > > >This e-mail, including attachments, may include confidential and/or >proprietary information, and may be used only by the person or entity to >which it is addressed. If the reader of this e-mail is not the intended >recipient or his or her authorized agent, the reader is hereby notified that >any dissemination, distribution or copying of this e-mail is prohibited. If >you have received this e-mail in error, please notify the sender by replying >to this message and delete this e-mail immediately. >-- >Please see the official ORACLE-L FAQ: http://www.orafaq.net >-- >Author: Michael Milligan > INET: [EMAIL PROTECTED] > >Fat City Network Services-- 858-538-5051 http://www.fatcity.com >San Diego, California-- Mailing list and web hosting services >- >To REMOVE yourself from this mailing list, send an E-Mail message >to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in >the message BODY, include a line containing: UNSUB ORACLE-L >(or the name of mailing list you want to be removed from). You may >also send the HELP command for other information (like subscribing).
RE: RE: Data Modeling opinion? Help?
Chris, I don't think anyone is disagreeing with your evaluation of what SHOULD be done (emphasis on purpose). But, you have to deal with the people and politics of the client. As I said before, it sounds like something else is going on in the organization, and someone decided to pull and end-around on you for some reason. I would personally be more concerned about why they felt that they had to do this to "get their way". Check your back, and make some friends (and maybe, learn the art of compromise? :) ) Tom Mercadante Oracle Certified Professional -Original Message- Sent: Tuesday, July 24, 2001 2:40 PM To: Multiple recipients of list ORACLE-L Hmmm...when the spec is changed because of some business requirement then that's fine. But when it's changed because your own designers cant argue the design on technical merit then what? A spec should quote all the business rules, and some high level details about the overall architecture of the system. But the spec shouldn't tell you that you will have these two specific tables in the database, with these specific fields, etc. In the end the contractor is ultimately responsible for the validity and performance of the system that they deliver. The contractor will never be able to point back to some disclaimer and say "We told you so". It will be next to impossible to point to the disclaimer when you start slipping the schedule or when the performance is not quite there. -Original Message- Sent: Tuesday, July 24, 2001 1:09 PM To: Grabowy; Chris; Multiple recipients of list ORACLE-L Chris, True, except when I as the customer change the specs. Then what is right is what I say. Or as a Program Management instructor told the class "As it is written, so let it be done." Dick Goulet Reply Separator Author: "Grabowy; Chris" <[EMAIL PROTECTED]> Date: 7/24/2001 9:48 AM Exactly. Which is why I am trying to change this now. As for the previous comment, they do not pay me to beat them over the head, BUT they do pay me to do what is right. -Original Message- Sent: Tuesday, July 24, 2001 1:29 PM To: Multiple recipients of list ORACLE-L Yes, but ironically enough, its the consultant they ram to the ground after it goes south, no matter how well you document that you recommended against it. -Original Message- Sent: Tuesday, July 24, 2001 10:02 AM To: Multiple recipients of list ORACLE-L Keep in mind that they pay you to advise them and to do what they want done. They do not pay you to beat them over the head to do what is right. Document to cya > This is one of those cases where I would document your > concerns and the > potential consequences thereof and submit that to damagement, > also keep a copy > for yourself in the 'Pearl Harbor File'. Then do as they > ask. Yeah, I know > it's dumb, but what are you as a consultant/contractor going to do? > > Dick Goulet -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Page, Bruce INET: [EMAIL PROTECTED] Fat City Network Services-- (858) 538-5051 FAX: (858) 538-5051 San Diego, California-- Public Internet access / Mailing Lists To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Kimberly Smith INET: [EMAIL PROTECTED] Fat City Network Services-- (858) 538-5051 FAX: (858) 538-5051 San Diego, California-- Public Internet access / Mailing Lists To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Grabowy, Chris INET: [EMAIL PROTECTED] Fat City Network Services-- (858) 538-5051 FAX: (858) 538-5051 San Diego, California-- Public Internet access / Mailing Lists To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). -- Please see the official ORACLE-L FAQ: http://www.orafaq.com
RE: RE: Data Modeling opinion? Help?
Hmmm...when the spec is changed because of some business requirement then that's fine. But when it's changed because your own designers cant argue the design on technical merit then what? A spec should quote all the business rules, and some high level details about the overall architecture of the system. But the spec shouldn't tell you that you will have these two specific tables in the database, with these specific fields, etc. In the end the contractor is ultimately responsible for the validity and performance of the system that they deliver. The contractor will never be able to point back to some disclaimer and say "We told you so". It will be next to impossible to point to the disclaimer when you start slipping the schedule or when the performance is not quite there. -Original Message- Sent: Tuesday, July 24, 2001 1:09 PM To: Grabowy; Chris; Multiple recipients of list ORACLE-L Chris, True, except when I as the customer change the specs. Then what is right is what I say. Or as a Program Management instructor told the class "As it is written, so let it be done." Dick Goulet Reply Separator Author: "Grabowy; Chris" <[EMAIL PROTECTED]> Date: 7/24/2001 9:48 AM Exactly. Which is why I am trying to change this now. As for the previous comment, they do not pay me to beat them over the head, BUT they do pay me to do what is right. -Original Message- Sent: Tuesday, July 24, 2001 1:29 PM To: Multiple recipients of list ORACLE-L Yes, but ironically enough, its the consultant they ram to the ground after it goes south, no matter how well you document that you recommended against it. -Original Message- Sent: Tuesday, July 24, 2001 10:02 AM To: Multiple recipients of list ORACLE-L Keep in mind that they pay you to advise them and to do what they want done. They do not pay you to beat them over the head to do what is right. Document to cya > This is one of those cases where I would document your > concerns and the > potential consequences thereof and submit that to damagement, > also keep a copy > for yourself in the 'Pearl Harbor File'. Then do as they > ask. Yeah, I know > it's dumb, but what are you as a consultant/contractor going to do? > > Dick Goulet -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Page, Bruce INET: [EMAIL PROTECTED] Fat City Network Services-- (858) 538-5051 FAX: (858) 538-5051 San Diego, California-- Public Internet access / Mailing Lists To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Kimberly Smith INET: [EMAIL PROTECTED] Fat City Network Services-- (858) 538-5051 FAX: (858) 538-5051 San Diego, California-- Public Internet access / Mailing Lists To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Grabowy, Chris INET: [EMAIL PROTECTED] Fat City Network Services-- (858) 538-5051 FAX: (858) 538-5051 San Diego, California-- Public Internet access / Mailing Lists To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Grabowy, Chris INET: [EMAIL PROTECTED] Fat City Network Services-- (858) 538-5051 FAX: (858) 538-5051 San Diego, California-- Public Internet access / Mailing Lists To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
