About
A level in a dimensional hierarchy is a set of attributes that has:
- an mandatory identifier attribute (known also as the business identifier)
- and descriptive attributes (optional)
Articles Related
Usage
A level is just metadata information that permits to:
- rewrite a dimensional query. (ie when a descriptif attribute is chosen, the query can be rewrite to use its identifier in order to fine an aggregate followed by a lookup to retrieve the descriptif attribute)
- define the grain of the query in order to see if there is an aggregate table that can serve it
Storage
In a relational database, the data of a level can be stored
- as an attribute subset of a the dimension table if the schema is a star schema
- as an apart table if the schema is a snowflake schema