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| metaperl... |
 Posted: Sun May 10, 2009 3:26 pm |
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Having used relational databases for about 10 years, I decided to take
an SAP course because I wanted to explore the idea of the star schema.
Weight was added to my interest when I learned SAP is the 4th largest
software company in the world. Further weight was added when everyone
I talked to said the pay was excellent.
Now I wish I had not paid for this course.
I am finding this very uncomfortable. I dont think the concepts are
clear and I think SAP is a rather rigid product. And I dont enjoy
trying to shoe-horn all the data in a warehouse into a central fact
table with several dimension tables. Of course the dimension tables
point to master data in the extended star schema, but that is a
performance enhancement.
I find the relational approach intuitive and flexible. The one
drawback that my co-workers cite is that you can get lots and lots of
tables. My counter to this is that as long as the tables have a nice
accurate UML diagram (can anyone recommend a tool for this sort of
modelling? preferably free) then you should be able to follow it with
ease. |
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| Terrence Brannon... |
| Posted: Sun May 10, 2009 3:33 pm |
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On May 10, 11:26 am, metaperl <metap... at (no spam) gmail.com> wrote:
Quote: And I dont enjoy
trying to shoe-horn all the data in a warehouse into a central fact
table with several dimension tables.
Let me be more concrete. An InfoCube (database) in SAP can have a
central fact table and 13 user-defined dimension tables relating to
it. You get a lot of automatic queries/reports generated for you by
adapting your data to this module. Not only that, but SAP comes with
time and unit (of measure) dimensions automatically. You can get
timestamping/tracking of data quite easily.
But why only 13 user-defined tables? You might end up stacking tons of
characteristics (attributes in dimensions tables) into a single
dimension table just to keep under 13.
If not that, then you might be forced to create a different InfoCube
and then create multicubes. |
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| Thomas Kellerer... |
| Posted: Sun May 10, 2009 7:52 pm |
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metaperl wrote on 10.05.2009 17:26:
Quote: I find the relational approach intuitive and flexible. The one
drawback that my co-workers cite is that you can get lots and lots of
tables. My counter to this is that as long as the tables have a nice
accurate UML diagram (can anyone recommend a tool for this sort of
modelling? preferably free) then you should be able to follow it with
ease.
You might want to try Power*Architect. It's a free and OpenSource ER Modeller
which is quite nice.
Note that you are looking for an ER (Entity Relationship) modelling tool, *not*
an UML tool.
Thomas |
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