best way to go w/code and database

ok so I am making a website for this company that wants to do transactions of orders and such; the company is a moving organization that arranges for the move, but doesnt do the move itself. So I had some questions:
I am working another programmer. But she is saying some things that I think aren't quite accurate but I just don't know.
she wants to use coldfusion for this project. I know php. I may be doing just the design anyway. I don't see any problem with cfm but I'm just setting this question up...
she says we need to go with microsoft sql server or oracle? I suggested mysql as it is cheaper and my friend had recomended it, and I use it myself. she was saying it may not have something that apparantly the others have, an up-to-the-moment backup? As far as I know, I can dump my mysql tables and such, but, can you recover something if it hasn't been dumped? some of these may be basic questions...
is cfm good with mysql? does it matter? Like I said I've only worked with php/mysql.
what kind of host should we be looking at? how much monthly traffic? I know these are questions that probably can't be answered with this little of info.
I would appreciate any articles, info, or suggestions about what the differences are between databases.

I think the argument she is trying to make is that MySQL isn't ACID compliant:

Atomicity - All elements of a given transaction take place or none do.

Consistency - Each transaction transforms the database from one valid state to another valid state.

Isolation - The effects of a transaction are not visible to other transactions in the system until it is complete.

Durability - Once a transaction has been committed, it's effects are permanent-- even if the system crashes, or a disk dies.

MySQL has this to say about their product:

http://www.mysql.com/press/release_2002_11.html

Basically if you use version 4.0, it comes with InnoDB tables as the standard feature, so you get ACID-compliant transactions out of the box.

If you want something even more robust than MySQL, yet still free, you might want to look at PostgreSQL. Some people say it's better, some even prefer it to Oracle. Depends on your project of course.

Is ACID commonly referred to as "rollback"?

Stumpy, my take is that rollbacks are a necessary product of ACID compliance.

Thecharking, I've never used cfm, but I know lots of developers scoff at it; that said, lots of developers also scoff at PHP or at Windows as a whole. As for what database management system to use, you're probably going to be pretty much at the mercy of whatever hosting company you choose. And most don't have Oracle just built in. Most'll give you mysql, I'd wager. As avit points out, mysql 4.0 does allow you to use transactions. MS SQL does as well, but your client had better be willing to pay some hefty licensing fees and probably to buy and set up a server. My guess is they're pretty small potatoes and aren't prepared to dedicate great resources to the project (no offense intended, but if this were a high priority for them, would they hire inexperienced developers? That's not a criticism of you but a question about the company's priorities and concern for their business systems.) I'm dubious about going with a Windows hosting group, as they're probably reluctant to keep servers patched, and your data might as well not be replicated if it's vulnerable anyway. I'd recommend looking for a host that'll run mysql 4 or postgresql.