Surrogate Keys

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Surrogate keys are used to join fact tables to dimensions. Surrogate keys isolate the data warehouse from changes to the operational systems, help in integrating data into dimensions coming from different sources and offer good performance when used in joins as they are simple integers. Lastly, they are used in tracking changes in dimension tables.

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Data Modeling

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Data modeling is the process of designing and validating a database that will be used to meet a business challenge. Data modelers use terms and symbols to identify and represent all of the data objects needed for a business operation to function.

Data models document entities (the persons, places and things [product, warehouse, partner etc.] an organization encounters in the course of business); the relationships of entities (e.g. employee WORKS in warehouse, MANAGES product and SHIPS to partner); and the attributes of entities (description, order number, address, account balance etc.).

There are three common types of data models.

Conceptual data models define and describe business concepts at a high level for stakeholders addressing a business challenge.

Logical data models are more detailed and describe entities, attributes and relationships in business terms.

Physical data models define database objects, schema and the actual columns and tables of data that will be created in the database.

Like the blueprint of a building, a data model is the design specification for a database. Data modeling can be helped by off the shelf data models that can be adapted to a specific use. But data architects warn that without proper time and attention to “design before you build,” organizations face inaccurate reporting, incorrect data, costly remediation and difficulty in meeting new user requirements.

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Real Time DW

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What I mean with real time DW here is: when the source system is updated, within few seconds that change is reflected in the DW. Generally speaking there are 3 ways to achieve this:

1) using a normalized data model,

2) using a dimensional data model and

3) keep the data in the source system.

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