Before talking about ways of loading dimension tables let us check how the data in dimension tables are. Loading depends on whether dimension stores historical data or not. If it’s not a changing dimension then simply insert. If it’s a changing dimension then we have,
Type 1: The new record replaces the original record. No trace of the old record exists.
Type 2: A new record is added into the customer dimension table. Thereby, the customer is treated essentially as two people.
Type 3: The original record is modified to reflect the change.
There are basically two types of Load
Before loading the data all the constraints will be disabled. After constraints are disabled data is loaded. Once loading is done the bad data is taken out and skipped from further process. This is faster method of loading
The data is loaded keeping data integrity (constraints).Here we don’t have to remove the constraints. This is slow method of loading.