I absolutely agree with sbarreda. Semantic layers are a great way of isolating the load process than the usage of the data which is generally designed together :( A 3NF data model gives better performnce while loading the data using Teradata load utilities and the Semantic layers gives better performance in data usage using Teradata best practices like Soft RIs, and other techniques.
People generally counter argue that when we have join indexes then why to use Physical tables in the semantic tables. I still prefer the physical ones given the reasons below.
1. JI take space and so do the physical tables.
2. Physical tables gives me more control on where to use them rather than relying upon the stats everytime to chose JIs.
3. Unlike the Join Indexes I can always query a physical table to get the data if required.
Thanks
↧