Best Practices for Designing and Implementing Data Warehouses
Published: 2023-05-15 21:45:58

## Introduction
Data warehousing has been embraced by organizations of all sizes.  The volume of data continues to grow as we populate our warehouses with increasingly atomic data and update them with greater frequency. Vendors continue to blanket the market with an ever-expanding set of tools to help us with data warehouse design, development, and usage. Most important, armed with access to our data warehouses, business professionals are making better decisions and generating payback on their data warehouse investments. 
A _data warehouse_ is a central repository of data integrated from multiple sources. When data gets loaded into the data warehouse, it is already modelled and structured for a specific purpose, it is analysis ready. Confusion over the roles of every component in the data warehouse environment is a major danger to its success. The four primary elements consist of:

**1. Operational Source Systems**
These are the operational record-keeping systems that log company transactions.

**2. Data Staging Area**
After the data has been moved to the staging area, it undergoes a variety of transformations, including cleansing, combining, deduplicating, and allocating warehouse keys.

**3. Data Presentation**
This is where data is structured, retained, and made accessible for direct querying by users, report authors, and other analytical applications.

**4. Data Access Tools**
A data access tool can be as simple as an ad hoc query tool or as complex as a sophisticated data mining or modeling application.

This article will delve into the recommended approaches to design and implement data warehouses that provide business value. 

## What do these practices entail?

**Define clear business requirements**
The first step in designing a data warehouse is to define clear business requirements. This includes understanding the types of data that need to be stored, the sources of that data, the frequency at which the data needs to be updated, and the types of queries that will be run against the data. It is important to involve business stakeholders in this process to ensure that the data warehouse meets their needs and supports their decision-making processes. 
When defining business requirements, it is also important to consider data quality. The data stored in the data warehouse should be accurate, complete, and consistent.

**Develop and maintain a project plan**
Creating a data warehouse project plan entails identifying all of the actions required to implement the data warehouse. The project plan should include a user acceptability checkpoint after each significant milestone and deliverable to ensure that the project remains on track and the company remains involved. Moreover, the data warehouse project demands broad communication.

**Choose the right data modelling approach**
The data modeling approach you choose will have a significant impact on the performance and scalability of your data warehouse. The two most common approaches are the star schema and the snowflake schema. 
The _star schema_ consists of a fact table that stores the primary information in the data warehouse and one or more dimension tables that provide additional context for the data in the fact table. The fact table and dimension tables are joined using foreign keys. 
The _snowflake schema_ is a more complex version of the star schema that allows for more efficient storage of data. In the snowflake schema, the dimension tables are normalized, which means that they are split into multiple tables. This allows for more efficient storage of data, but it also makes the schema more complex to implement and query. 
When choosing a data modeling approach, consider <u>the complexity of your data, the types of queries you will be running, and the scalability requirements of your data warehouse</u>.

**Use an ETL tool for data integration** 
Data integration is a critical part of any data warehouse implementation. ETL (extract, transform, load) tools are commonly used for data integration, and they can significantly reduce the time and effort required to integrate data from multiple sources. When choosing an ETL tool, look for one that supports the sources and targets you need, has good performance and scalability, and is easy to use and maintain. 
In addition to ETL tools, consider using data virtualization tools for real-time data integration. Data virtualization tools allow you to access and integrate data from multiple sources in real time without having to replicate the data in a data warehouse.

**Optimize data loading and querying**
Data loading and querying are two of the most performance-critical areas of a data warehouse. To optimize data loading, consider using bulk loading techniques and optimizing the data structures used for staging and loading data. Bulk loading techniques, such as the _COPY_ command in Amazon Redshift, can significantly reduce the time and effort required to load data into a data warehouse. 
To optimize querying, consider using indexes, pre-aggregations, and partitioning. Indexes can significantly improve query performance by allowing the database to quickly find the relevant data. Pre-aggregations are summary tables that are precomputed to speed up queries that require aggregations.

**Ensure data security and privacy** 
Data security and privacy are critical considerations for any data warehouse implementation. The data stored in the data warehouse may contain sensitive information about customers, employees, and the business itself. It is important to implement security measures to protect this data from unauthorized access and ensure that it is used only for its intended purposes. 
One of the best ways to ensure data security and privacy is to implement a robust access control system. This involves defining roles and permissions for users and groups, and ensuring that only authorized users have access to sensitive data. It is also important to encrypt sensitive data both in transit and at rest to protect it from unauthorized access. 
In addition to access control and encryption, consider implementing auditing and monitoring tools to track access to the data warehouse and identify any potential security breaches. Regular security assessments and penetration testing can also help identify vulnerabilities in the data warehouse and address them before they can be exploited.

## What are some mistakes to steer clear of?

- <u>Relying on consultants or internal experts to interpret the users' data warehouse requirements, instead of engaging the business users.</u>- The success of a data warehouse project is measured by how you serve the business user's needs.

- <u>Delaying the involvement of senior executives in the data warehouse implementation process until after it has been successfully deployed and its impact can be demonstrated.</u>- For the data warehouse to be utilized effectively, top executives should be updated of the progress from the very beginning, for you to get their support.

- <u>Considering the assumption that business users have a natural tendency to be drawn to comprehensive data and create their own impactful analytical applications.</u>- Business users are typically not skilled in application development. They are more likely to adopt the use of a data warehouse if it comes equipped with a range of pre-designed analytical applications that are readily available for their use.

- <u>Meeting to plan and discuss communication with the business users once the data warehouse is implemented.</u>- Conducting training sessions and providing continuous personal support to the business community ought to be essential requirements before the initial implementation of the data warehouse.

## Conclusion
In modern data-driven organizations, data warehouses play a critical role. However, designing and implementing a data warehouse that caters to the needs of the business can be challenging due to complex data and ever-changing requirements. To ensure the successful implementation of a data warehouse, it is important to follow best practices such as involving business stakeholders in the design process, developing a project plan, choosing the right data modeling approach, using appropriate tools for data integration, optimizing data loading and querying, and implementing robust security measures to protect sensitive data. By following these practices, you can design and implement a data warehouse that delivers value to the business while ensuring data security and privacy.