Re: problems with nextId

On Fri, 16 Aug 2002 12:10:13 -0500 "Matt McDonald" <matt@coffeecup.com> wrote: > Thanks for the help, I think I'm starting to get somewhere, but I'm still > not fully understanding where the problem is. FYI, I'm using MySQL 3.23.39 > I gave the account full database permissions, then tried your script listed > below, and came back with this: > > An error has occured: DB Error: DB backend not capable > > So is it my version of MySQL the problem (it's fairly close to the latest > stable version available), or is it the way I have my tables configured? It´s highly unlikely that MySQL is the problem here. It seems you have a _very_ old version of PEAR::DB - check http://pear.php.net/ for the latest version. > I'm still kind of confused how sequences work. Right now, I've got 22 > tables set up in by database. So when I call nextId to set up a new > sequence, does it scan all tables and come up with a value that would work > no matter what table I insert into? If that is the case, perhaps there is a > table I have configured that stumps the scanning process? No tables are scanned. It´s really not that complicated. If you call $newId = $db->nextId("mySequence"); ...PEAR::DB looks if a Sequence called "mySequence" exists. If yes, it will get a new value from the sequence. If the sequence doesn´t exist, PEAR::DB will try to create a new one called "mySequence", which will start with the value 1. So, if you always fetch your IDs for a Table from the same sequence, you´ll always have unique IDs. It´s pretty much the same as having an auto_increment value in your table, but the same sequence can also be used by multiple tables. As MySQL doesn´t support sequences natively, PEAR::DB emulates them by creating a table for each new sequence that has only one column, which is an auto_increment value. Anytime you call nextId(), PEAR::DB will insert a new value in the table and return the ID that was generated. Other databases, like PostgreSQL or Oracle, handle sequences natively, so no emulation is needed there. Regards, Markus -- Markus Wolff <wolff@21st.de>