Best way to build a DataMart from multiple external systems?

I'm in the planning stages of building a SQL Server DataMart for mail/e开发者_开发问答mail/SMS contact info and history. Each piece of data is located in a different external system. Because of this, email addresses do not have account numbers and SMS phone numbers do not have email addresses, etc. In other words, there isn't a shared primary key. Some data overlaps, but there isn't much I can do except keep the most complete version when duplicates arise.

Is there a best practice for building a DataMart with this data? Would it be an acceptable practice to create a key table with a column for each external key? Then, a unique primary ID can be assigned to tie this to other DataMart tables.

Looking for ideas/suggestions on approaches I may not have yet thought of.

Thanks.

The email address or phone number itself sounds like a suitable business key. Typically a "staging" database is used to load the data from multiple sources and then assign surrogate keys and do other transformations.

Are you familiar with data warehouse methods and design patterns? If you don't have previous knowledge or experience then consider hiring some help. BI / data warehouse projects have a very high failure rate and mistakes can be expensive.

Found more information here:

http://en.wikipedia.org/wiki/Extract,_transform,_load#Dealing_with_keys

Well, with no other information to tie the disparate pieces together, your datamart is going to be pretty rudimentary. You'll be able to get the types of data (sms, email, mail), metrics for each type over time ("this week/month/quarter/year we averaged 42.5 sms texts per day, and 8000 emails per month! w00t!"). With just phone numbers and email addresses, your "other datamarts" will likely have to be phone company names, or internet domains. I guess you could link from that into some sort of geographical information (internet provider locations?), or maybe financial information for the companies. Kind of a blur if you don't already know which direction you want to head.

To be honest, this sounds like someone high-up is having a knee-jerk reaction to the "datamart" buzzword coupled with hearing something about how important communication metrics are, so they sent orders on down the chain to "get us some datamarts to run stats on all our e-mails!"

You need to figure out what it is that you or your employer is expecting to get out of this project, and then figure out if the data you're currently collecting gives you a trail to follow to that information. Right now it sounds like you're doing it backwards ("I have this data, what's it good for?"). It's entirely possible that you don't currently have the data you need, which means you'll need to buy it (who knows if you could) or start collecting it, in which case you won't have nice looking graphs and trend-lines for upper-management to look at for some time... falling right in line with the warning dportas gave you in his second paragraph ;)