RE: [PHP-DB] transaction locking
Hi ALek, Yes you can make the column auto_increment. YOu can also make the incrementations start at a particular value by using the ALTER command. EG: ALTER TABLE mytable AUTO_INCREMENT = 99; it will start your next inserted record with 99 for that specific column value. I am not 100% sure about the values that you already have in your field. I assume that they are all unique and that you want to start the increment from the last value +1. anyway hope this helps. Angelo Disclaimer This e-mail transmission contains confidential information, which is the property of the sender. The information in this e-mail or attachments thereto is intended for the attention and use only of the addressee. Should you have received this e-mail in error, please delete and destroy it and any attachments thereto immediately. Under no circumstances will the Cape Technikon or the sender of this e-mail be liable to any party for any direct, indirect, special or other consequential damages for any use of this e-mail. For the detailed e-mail disclaimer please refer to http://www.ctech.ac.za/polic or call +27 (0)21 460 3911 -- PHP Database Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP-DB] transaction locking
Aleks Kalynovych wrote: I have a couple forms that generate a unique ID based on taking the highest number in the ID column adding 1 to its value. The problem is that I dont save that number until the form is submitted. If 2 or more persons fill out the form at the same time they all get the same ID number. I hope that there are some suggestions on how to accomplish this with a better method What database are you using? Pretty much all of them have a method for generating these numbers internally. Consult your documentation. -- ---John Holmes... Amazon Wishlist: www.amazon.com/o/registry/3BEXC84AB3A5E/ php|architect: The Magazine for PHP Professionals www.phparch.com -- PHP Database Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP-DB] transaction locking
Aleks, Many programmers learned the hard way that the scheme you are proposing did not work when they went from a single user to a networked environment. You've not said what database you are using. If MySQL you can let it's autoincrement increase your key automatically, perhaps feed it back as confirmation of completion. Using this you will not get duplicates as the insert is unique per connection. Check the MySQL docs for the last insert id. Try this - it works and takes a load off your code. Alternately, if you want to use your own scheme, establish a lookup table with two fields: keyvalue and tablename. Write a function that with the table name as a parameter, locks the table, retrieves the keyvalue, adds one to it, updates and exits. You will have to test for locks, you may end up with gaps in your key numbers. If possible, let the database do the work for you. Regards - Miles Thompson At 06:11 AM 12/5/2003 -0700, Aleks Kalynovych wrote: Good morning all, I have a couple forms that generate a unique ID based on taking the highest number in the ID column adding 1 to its value. The problem is that I don’t save that number until the form is submitted. If 2 or more persons fill out the form at the same time they all get the same ID number. I hope that there are some suggestions on how to accomplish this with a better method TIA for your help Aleks -- PHP Database Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php -- PHP Database Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
RE: [PHP-DB] transaction locking
Thanks Miles and John for you answers... Yes I am using MySQL. I think I can work it to use the dB to generate these. I ran into The problem originally because this dB was taking up where a different Tool was ending and I needed to start with a specific number scheme. Here Is a though... If I have a field in MySQL that had numbers already populated Along with an auto incremental column... Can I remove this auto column and Change the properties of the already populated column to auto generate? Will It accept the numbers already there or will I have to start from scratch? In other words I know that in the dB if you setup a new table and set a column\ To auto increment, it starts a the number 1. Can this be set to a higher number Say 5454 ?? TIA Aleks -Original Message- From: Miles Thompson [mailto:[EMAIL PROTECTED] Sent: Friday, December 05, 2003 8:24 AM To: [EMAIL PROTECTED] Subject: Re: [PHP-DB] transaction locking Aleks, Many programmers learned the hard way that the scheme you are proposing did not work when they went from a single user to a networked environment. You've not said what database you are using. If MySQL you can let it's autoincrement increase your key automatically, perhaps feed it back as confirmation of completion. Using this you will not get duplicates as the insert is unique per connection. Check the MySQL docs for the last insert id. Try this - it works and takes a load off your code. Alternately, if you want to use your own scheme, establish a lookup table with two fields: keyvalue and tablename. Write a function that with the table name as a parameter, locks the table, retrieves the keyvalue, adds one to it, updates and exits. You will have to test for locks, you may end up with gaps in your key numbers. If possible, let the database do the work for you. Regards - Miles Thompson At 06:11 AM 12/5/2003 -0700, Aleks Kalynovych wrote: Good morning all, I have a couple forms that generate a unique ID based on taking the highest number in the ID column adding 1 to its value. The problem is that I don’t save that number until the form is submitted. If 2 or more persons fill out the form at the same time they all get the same ID number. I hope that there are some suggestions on how to accomplish this with a better method TIA for your help Aleks -- PHP Database Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php -- PHP Database Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php -- PHP Database Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
RE: [PHP-DB] transaction locking
Hi, Aleks Kalynovych wrote: I have a couple forms that generate a unique ID based on taking the highest number in the ID column adding 1 to its value. The problem is that I dont save that number until the form is submitted. If 2 or more persons fill out the form at the same time they all get the same ID number. I hope that there are some suggestions on how to accomplish this with a better method You really should avoid using this method precisely because of the concurrency issue that will invariably happen. If you're using MySQL and your ID field is of type AUTO_INCREMENT then you can use MySQL built-in method named: LAST_INSERT_ID() or in PHP you can use a function named: mysql_insert_id() http://www.php.net/mysql_insert_id For more information visit: http://www.mysql.com/doc/en/example-AUTO_INCREMENT.html This is concurrency safe so you shouldn't have this problem in the future. HTH -- PHP Database Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
RE: [PHP-DB] transaction locking
Aleks, Every time I've dumped and moved a database with autoincrement fields the numbering has picked up where it left off. Dump the database, including the data, adjust the field type in the database schema, and reload. Regards - Miles At 09:36 AM 12/5/2003 -0500, Aleks K wrote: Thanks Miles and John for you answers... Yes I am using MySQL. I think I can work it to use the dB to generate these. I ran into The problem originally because this dB was taking up where a different Tool was ending and I needed to start with a specific number scheme. Here Is a though... If I have a field in MySQL that had numbers already populated Along with an auto incremental column... Can I remove this auto column and Change the properties of the already populated column to auto generate? Will It accept the numbers already there or will I have to start from scratch? In other words I know that in the dB if you setup a new table and set a column\ To auto increment, it starts a the number 1. Can this be set to a higher number Say 5454 ?? TIA Aleks -Original Message- From: Miles Thompson [mailto:[EMAIL PROTECTED] Sent: Friday, December 05, 2003 8:24 AM To: [EMAIL PROTECTED] Subject: Re: [PHP-DB] transaction locking Aleks, Many programmers learned the hard way that the scheme you are proposing did not work when they went from a single user to a networked environment. You've not said what database you are using. If MySQL you can let it's autoincrement increase your key automatically, perhaps feed it back as confirmation of completion. Using this you will not get duplicates as the insert is unique per connection. Check the MySQL docs for the last insert id. Try this - it works and takes a load off your code. Alternately, if you want to use your own scheme, establish a lookup table with two fields: keyvalue and tablename. Write a function that with the table name as a parameter, locks the table, retrieves the keyvalue, adds one to it, updates and exits. You will have to test for locks, you may end up with gaps in your key numbers. If possible, let the database do the work for you. Regards - Miles Thompson At 06:11 AM 12/5/2003 -0700, Aleks Kalynovych wrote: Good morning all, I have a couple forms that generate a unique ID based on taking the highest number in the ID column adding 1 to its value. The problem is that I don’t save that number until the form is submitted. If 2 or more persons fill out the form at the same time they all get the same ID number. I hope that there are some suggestions on how to accomplish this with a better method TIA for your help Aleks -- PHP Database Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php -- PHP Database Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php -- PHP Database Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php -- PHP Database Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
