verification upon update, help, please
Does MySQL prevent updates from occurring when the values involved are the same as the database's current state. For instance, if I've got a table create table updater( id int not null primary key auto_increment, is_active int not null default 1 }; insert into updater(is_active) values (1); insert into updater(is_active) values (1); update updater set is_active = 1; Would MySQL essentially disregard this update statement b/c the values contained within the table are already 1? Now, I realize that the values wouldn't be altered, but does the dB do pre-checking and see which (if any) rows would be affected by the query, and only run the update against rows that would be changed? There seems to be some reporting that is displayed which indicates that MySQL DOES indeed to pre-checking mysql select * from updater; ++---+ | id | is_active | ++---+ | 1 | 1 | | 2 | 1 | ++---+ 2 rows in set (0.00 sec) mysql update updater set is_active = 1; Query OK, 0 rows affected (0.00 sec) Rows matched: 2 Changed: 0 Warnings: 0 mysql any thoughts? thanks, Paul _ MSN Photos is the easiest way to share and print your photos: http://photos.msn.com/support/worldwide.aspx - Before posting, please check: http://www.mysql.com/manual.php (the manual) http://lists.mysql.com/ (the list archive) To request this thread, e-mail [EMAIL PROTECTED] To unsubscribe, e-mail [EMAIL PROTECTED] Trouble unsubscribing? Try: http://lists.mysql.com/php/unsubscribe.php
Re: verification upon update, help, please
At 12:07 -0400 7/3/02, Paul Tomsic wrote: Does MySQL prevent updates from occurring when the values involved are the same as the database's current state. I don't know if prevent is the word exactly. It doesn't bother to update the row unless you actually change a value. The phenonenon you're observing is that the row-count value means rows actually changed from their current values rather than rows select to be updated. For instance, if I've got a table create table updater( id int not null primary key auto_increment, is_active int not null default 1 }; insert into updater(is_active) values (1); insert into updater(is_active) values (1); update updater set is_active = 1; Would MySQL essentially disregard this update statement b/c the values contained within the table are already 1? Now, I realize that the values wouldn't be altered, but does the dB do pre-checking and see which (if any) rows would be affected by the query, and only run the update against rows that would be changed? There seems to be some reporting that is displayed which indicates that MySQL DOES indeed to pre-checking mysql select * from updater; ++---+ | id | is_active | ++---+ | 1 | 1 | | 2 | 1 | ++---+ 2 rows in set (0.00 sec) mysql update updater set is_active = 1; Query OK, 0 rows affected (0.00 sec) Rows matched: 2 Changed: 0 Warnings: 0 mysql any thoughts? thanks, Paul - Before posting, please check: http://www.mysql.com/manual.php (the manual) http://lists.mysql.com/ (the list archive) To request this thread, e-mail [EMAIL PROTECTED] To unsubscribe, e-mail [EMAIL PROTECTED] Trouble unsubscribing? Try: http://lists.mysql.com/php/unsubscribe.php
RE: verification upon update, help, please
What happens if you put third TIMESTAMP column.?. Will that be updated?. Just curios. Nilesh -Original Message- From: Paul DuBois [mailto:[EMAIL PROTECTED]] Sent: Wednesday, July 03, 2002 12:42 PM To: Paul Tomsic; [EMAIL PROTECTED] Subject: Re: verification upon update, help, please At 12:07 -0400 7/3/02, Paul Tomsic wrote: Does MySQL prevent updates from occurring when the values involved are the same as the database's current state. I don't know if prevent is the word exactly. It doesn't bother to update the row unless you actually change a value. The phenonenon you're observing is that the row-count value means rows actually changed from their current values rather than rows select to be updated. For instance, if I've got a table create table updater( id int not null primary key auto_increment, is_active int not null default 1 }; insert into updater(is_active) values (1); insert into updater(is_active) values (1); update updater set is_active = 1; Would MySQL essentially disregard this update statement b/c the values contained within the table are already 1? Now, I realize that the values wouldn't be altered, but does the dB do pre-checking and see which (if any) rows would be affected by the query, and only run the update against rows that would be changed? There seems to be some reporting that is displayed which indicates that MySQL DOES indeed to pre-checking mysql select * from updater; ++---+ | id | is_active | ++---+ | 1 | 1 | | 2 | 1 | ++---+ 2 rows in set (0.00 sec) mysql update updater set is_active = 1; Query OK, 0 rows affected (0.00 sec) Rows matched: 2 Changed: 0 Warnings: 0 mysql any thoughts? thanks, Paul - Before posting, please check: http://www.mysql.com/manual.php (the manual) http://lists.mysql.com/ (the list archive) To request this thread, e-mail [EMAIL PROTECTED] To unsubscribe, e-mail [EMAIL PROTECTED] Trouble unsubscribing? Try: http://lists.mysql.com/php/unsubscribe.php - Before posting, please check: http://www.mysql.com/manual.php (the manual) http://lists.mysql.com/ (the list archive) To request this thread, e-mail [EMAIL PROTECTED] To unsubscribe, e-mail [EMAIL PROTECTED] Trouble unsubscribing? Try: http://lists.mysql.com/php/unsubscribe.php
