Important information about databases.

Construction of the relational model.

1. Define all the necessary tables.

2. Establish relationships and cardinality.

3. Normalize to the third normal form.

4. Normalize without inferring.

5. Cross table to avoid duplicity. It is used when there are many to many relationships.

 

Data warehouse.

Data warehouse. It is a database oriented to planning.

Characteristics.

1. Oriented to theme

2. Variation in time

3. Non-volatile

Function. Keep data that can be analyzed quickly for consultation without affecting the work.

The data must be separated from those that are entered and what will be used for storage. From this functionality is derived:

ETL: Extraction, Transformation and loading. With this the information is not anchored to the Perse Database.

* Data marts Departmental data that feed from the Data Warehouse. The cubes are contemplated for the analysis of the data.

Schemas of data warehouse.

Star scheme. The most basic, since it is based on a table of facts and surrounded by dimension tables. Your primary keys are placed on the facts table. Mitigate going to all dimension tables.

Snowflake outline. Meets the third normal way. Saves table in memory and is based on the relational model. The common elements are obtained. Query statements increase complexity.

Constellation scheme. Much more complex, since there are multiple fact tables. It is difficult to maintain on a future scale.