Basic questions regarding Data Warehousing

Question

I'm wanting to use OLAP cubes and have to first design a data warehouse. I am going for the star-schema. I'm a little confused about how to convert from a normal database to a data warehouse, especially with regards to foreign keys between dimension tables. I know a fact table has foreign keys to dimensions, but do dimensions have foreign keys between them? For example, what do I need to do with the following 2 examples:

TABLE: Airports
COLUMNS: Id, Name, Code, CityId

When I make the Airports dimension, do I remove CityId and put the City Name instead? Or what?

TABLE: Regions
COLUMNS: Id, Name, RegionType, ParentId

The question for this one is mostly the same, but a bit more complex, because here ParentId refers to the same table (Regions).. example: a City can refer to a parent Country record. How do I translate these over to a data warehouse star schema?

Lastly, regarding measures, those go on the fact table, right? I think I will likely need multiple fact tables. Is that normal? Does one fact table translate to one OLAP cube? Or what?

Answer 1

You want to include city within your airport dimension. You are intentionally flattening out your normalised schema to aid the speed of the dimensional model which can seem counter intuitive if you are coming from transactional development.

With regards to the perennial child relationship, you want the parented to be translated into the surrogate of the region record. Ssas will provide the functionality to relate parent child records when you are designing your cube.

Multiple facts are not unusual, but unless the fact data is completely unrelated, there is no need to separate them into different cubes. The requirement for multiple facts will be driven by having data at a different grain. Keep all of you metrics (I.e. Flights) together, but you would separate out flight metrics from food sale metrics

Answer 2

you not converting to data warehouse, you are creating new data warehouse with few dimension and 1 (at least) Fact table. dimension tables are loaded first and you DO NOT want to change id with name. you need additional key for each dimension table. once you load dimensions, I usually use ssis package to load fact table.(either incremental load or you can truncate fact table each time before you load with new data( depends what you need) ...