1) ER model is 2 dimensional, Star Schema is MDM.
2) ER model is Normalized, Star Schema is Denormalized.
* Limitataions of Star Schema :-
1) No Reusability of Master Data
Since the Master Data table is acting as the Dimension table which is inside the cube, So the Master data table cannot be reused.
2) Degraded Performance :
* The processing of numerics is much faster when compared to processing of Alpha Numerics, Since all the tables inside the cube contains Alpha Numeric values it degrades the performance of the queries.
3) Limited Analysis:
Maximum no. of Characteristics in a Fact table is : 16, Since each characteristic coloumn in the fact table connects to one Dimension table/Master data Table, So max no. of Dimension tables what we can have is limited 16.