[PHP-DB] DB Design Concepts
I'm using MySQL 5.x InnoDB engine, transactional tables. I have a conceptual design question. If I have a two columns 'a' and 'b', a is the primary key, and b is a type double, in table 1 (T1) for which column b will have many NULL values, do I leave it with an allow null constraint on the column or pull the column and place it into table 2 (T2) with a foreign key, making a simple optional one-to-one relationship. Over the course of time, as the table fills with records, will a column w/ many NULL values have a detrimental effect on performance or maintenance with regards to the DB? Am I missing something here in DB design 101, by leaving the column in the T1 and knowing it will only be populated 7% of the time; what are the major implications based on the RDBMS and engine I'm using? Do I go to 2nd NF simply because a column is not going to be populated as often? Max H. Thayer Lead Software Developer Center for High-Throughput Structural Biology Hauptman-Woodward Medical Research Inst. 700 Ellicott St. Buffalo, NY 14203 Phone: 716-898-8637 Fax: 716-898-8660 http://www.chtsb.org http://www.chtsb.org/ http://www.hwi.buffalo.edu http://www.hwi.buffalo.edu/
RE: [PHP-DB] DB Design Concepts
That's one of the kickers. The 7% of the time the column is populated is determined by business logic. And when the business logic says it's needed, at application run time if certain conditions were met, the column takes on the characteristic NOT NULL attribute. -Original Message- From: Dan Shirah [mailto:[EMAIL PROTECTED] Sent: Wednesday, May 02, 2007 3:50 PM To: Max Thayer Cc: php-db@lists.php.net Subject: Re: [PHP-DB] DB Design Concepts Max, I am assuming that since column b will only be populated 7% of the time that it is not a value specific column (does not matter if it has a value or not) Therefore I would suggest leaving the NULL's in there as it will not (at least should not) affect any system performance. On 5/2/07, Max Thayer [EMAIL PROTECTED] wrote: I'm using MySQL 5.x InnoDB engine, transactional tables. I have a conceptual design question. If I have a two columns 'a' and 'b', a is the primary key, and b is a type double, in table 1 (T1) for which column b will have many NULL values, do I leave it with an allow null constraint on the column or pull the column and place it into table 2 (T2) with a foreign key, making a simple optional one-to-one relationship. Over the course of time, as the table fills with records, will a column w/ many NULL values have a detrimental effect on performance or maintenance with regards to the DB? Am I missing something here in DB design 101, by leaving the column in the T1 and knowing it will only be populated 7% of the time; what are the major implications based on the RDBMS and engine I'm using? Do I go to 2nd NF simply because a column is not going to be populated as often? Max H. Thayer Lead Software Developer Center for High-Throughput Structural Biology Hauptman-Woodward Medical Research Inst. 700 Ellicott St. Buffalo, NY 14203 Phone: 716-898-8637 Fax: 716-898-8660 http://www.chtsb.org http://www.chtsb.org/ http://www.hwi.buffalo.edu http://www.hwi.buffalo.edu http://www.hwi.buffalo.edu/ -- PHP Database Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP-DB] DB Design Concepts
Okay, so couldn't you just set a default value for the column (N for NULL). This way column 1 and column 2 both contain valid data for whichever state your column takes on. Then just tell your logic to omit the results of column 2 that have a value of N. This way only your valid rows would be pulled and your value for N would serve the purpose of a NULL as your logic changes the state. On 5/2/07, Max Thayer [EMAIL PROTECTED] wrote: That's one of the kickers. The 7% of the time the column is populated is determined by business logic. And when the business logic says it's needed, at application run time if certain conditions were met, the column takes on the characteristic NOT NULL attribute. -Original Message- From: Dan Shirah [mailto:[EMAIL PROTECTED] Sent: Wednesday, May 02, 2007 3:50 PM To: Max Thayer Cc: php-db@lists.php.net Subject: Re: [PHP-DB] DB Design Concepts Max, I am assuming that since column b will only be populated 7% of the time that it is not a value specific column (does not matter if it has a value or not) Therefore I would suggest leaving the NULL's in there as it will not (at least should not) affect any system performance. On 5/2/07, Max Thayer [EMAIL PROTECTED] wrote: I'm using MySQL 5.x InnoDB engine, transactional tables. I have a conceptual design question. If I have a two columns 'a' and 'b', a is the primary key, and b is a type double, in table 1 (T1) for which column b will have many NULL values, do I leave it with an allow null constraint on the column or pull the column and place it into table 2 (T2) with a foreign key, making a simple optional one-to-one relationship. Over the course of time, as the table fills with records, will a column w/ many NULL values have a detrimental effect on performance or maintenance with regards to the DB? Am I missing something here in DB design 101, by leaving the column in the T1 and knowing it will only be populated 7% of the time; what are the major implications based on the RDBMS and engine I'm using? Do I go to 2nd NF simply because a column is not going to be populated as often? Max H. Thayer Lead Software Developer Center for High-Throughput Structural Biology Hauptman-Woodward Medical Research Inst. 700 Ellicott St. Buffalo, NY 14203 Phone: 716-898-8637 Fax: 716-898-8660 http://www.chtsb.org http://www.chtsb.org/ http://www.hwi.buffalo.edu http://www.hwi.buffalo.edu http://www.hwi.buffalo.edu/
Re: [PHP-DB] DB Design Concepts
Max Thayer wrote: I'm using MySQL 5.x InnoDB engine, transactional tables. I have a conceptual design question. If I have a two columns 'a' and 'b', a is the primary key, and b is a type double, in table 1 (T1) for which column b will have many NULL values, do I leave it with an allow null constraint on the column or pull the column and place it into table 2 (T2) with a foreign key, making a simple optional one-to-one relationship. Over the course of time, as the table fills with records, will a column w/ many NULL values have a detrimental effect on performance or maintenance with regards to the DB? Am I missing something here in DB design 101, by leaving the column in the T1 and knowing it will only be populated 7% of the time; what are the major implications based on the RDBMS and engine I'm using? What kind of queries are you going to be running? Where you need both columns all the time? I'd suggest leaving them in the same table for a few reasons: - If you're always joining the two tables there's no point in having them separate. - If you always need the NULL entries, you're going to have to LEFT OUTER JOIN the two tables every time because table '1' will have an entry but table '2' might not. - You're going to gain performance with large datasets because the database (mysql or any other type) doesn't have to join two tables and match up entries and so on. If on the other hand you are going to have a script that runs once a month that queries both tables, this is all moot. Is there another way you can do what you want? eg a stored procedure? http://dev.mysql.com/doc/refman/5.0/en/stored-procedures.html -- Postgresql php tutorials http://www.designmagick.com/ -- PHP Database Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP-DB] DB Design Concepts
actualy i'm not soo smart.. Max Thayer wrote: I'm using MySQL 5.x InnoDB engine, transactional tables. I have a conceptual design question. If I have a two columns 'a' and 'b', a is the primary key, and b is a type double, in table 1 (T1) for which column b will have many NULL values, do I leave it with an allow null constraint on the column or pull the column and place it into table 2 (T2) with a foreign key, making a simple optional one-to-one relationship. Over the course of time, as the table fills with records, will a column w/ many NULL values have a detrimental effect on performance or maintenance with regards to the DB? Am I missing something here in DB design 101, by leaving the column in the T1 and knowing it will only be populated 7% of the time; what are the major implications based on the RDBMS and engine I'm using? can we see your table?? u can use my way for your problem. if you have access.. the lowest is fine. I create the table from there and then i use relationship. What kind of queries are you going to be running? Where you need both columns all the time? i ask same things.. hope my zip can help u -- PHP Database Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
