数仓概念 | 逻辑 | 物理模型

Conceptual Data Model

A Data warehouse conceptual data model is nothing but a highest-level relationships between the different entities (in other word different table) in the data model.

the features of conceptual data model

Following are the features of conceptual data model:

• This is initial or high level relation between different entities in the data model.
• Conceptual model includes the important entities and the relationships among them.
• In the Data warehouse conceptual data model you will not specify any attributes to the entities.
• You also not define any primary key yet.

From the above table you can see that, data warehouse conceptual model, only high level relationship between the entities are described.

Logical Data Model

A Data warehouse logical data model describes model in more detail compared to the Data Warehouse conceptual data model. A data warehouse logical data model describes the data in as much detail as possible, this model does not describe how the model is implemented.

Following are the features of conceptual data model

• This model includes all entities in the model and relationships among them.
• You should specify the attributes for each entities in the model
• You should also specify the primary key (if database supports) at this stage
• Foreign keys are also specified. Primary and foreign keys are used to define the relation between the entities
  Normalization occurs at this level. You have to normalize the table in case if that is required during logical model design

Schematic Representation of Data Warehouse Logical Data Model

The figure below is an example of a logical data model:

From the above table you can see that, data warehouse logical model describes the entities as much as possible.

Data Warehouse Physical Data Model

The Data warehouse physical data model describes how the model will be built in the database. A physical database model shows all table structures, including column name, column data type, column constraints, primary key, foreign key, and relationships between tables.

Features of Data Warehouse Physical Data Model

Following are the features of conceptual Physical model:

• In this model you will Specify all tables and columns that are available in the model
• You will use the foreign keys to identify relationships between tables in the model
• You may want to denormalize tables based on user requirements. Denormalization will speed up the data retrieval mechanism
• Physical considerations may cause the physical data model to be quite different from the logical data model
• Physical data model will be different for different RDBMS. For example, RDBMS like Oracle, SQL use the Primary and foreign keys whereas Netezza does not use. You may want to generate the tabe structure specific to that RDBMS

Schematic Representation of Data Warehouse Physical Data Model

The figure below is an example of a physical data model.

From the above diagram you can see that, data warehouse physical model describes how the tables are actually created in the data warehouse environment.

转自：https://dwgeek.com/data-warehouse-physical-data-model.html/