For a
Datawarehouse project ,the client will define their business requirement and
functionality of their business.Once this stage is over we need to design the
logical and physical part of Datawarehouse.
First
lets talk about the Logical design.During
the logical design phase, you defined a model for your data warehouse
consisting of entities, attributes, and relationships.We deal only with
defining the types of information that you need.Here we check for the logical
relationship among objects.
The
process of logical design involves arranging data into a series of logical
relationships called entities and attributes. An entity represents a
chunk of Data Warehousing Schemas information. . An attribute is a
component of an entity that helps define the uniqueness of the entity. In
relational databases, an attribute maps to a column.Also there is a unique identifier to define each
records uniquely.
During
the Physical design process, we
convert the logical design into physical by using database structures. At this
time, you have to map:
- Entities to tables
- Relationships to foreign key constraints
- Attributes to columns
- Primary unique identifiers to primary key constraints
- Unique identifiers to unique key constraints
Once
the physical design is made we need to create some the below structures:
- Tablespaces:It’s a collection of datafiles.Each table belongs to a tablespace.
- Tables and Partitioned Tables: Using partitioned tables instead of nonpartitioned ones addresses the key problemof supporting very large data volumes by allowing you to decompose them into smaller and more manageable pieces.
- Views: It’s a collection of one or more tables or views
- Integrity Constraints: Its used to enforce the business constraints such as Not null for employee id
- Dimensions: A dimension is a schema object that defines hierarchical relationships between columns or column sets
By
building a datawarehouse in this way we can make a design that allows for
growth and changes as the needs ofusers change and evolve.
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