Understanding Data

Chapter 3 describes the sources and nature of data in some detail: how data is generated and what affects data quality. Data may originate from transaction systems, sensors, social media sites, or crowdsourcing. It comes in different forms, such as structured and unstructured data; it may be updated in real time or periodically and may have variable accuracy. The nature of the source, whether it be a person or device, is relevant to understand the type of processing and analysis that will be conducted. Also, the method of collection, whether it be through survey, sensor, or third-party aggregator, affects the completeness and representativeness of the data, which in turn impacts the reliability of any insights drawn from it.


Chapter 4 looks into the destination of data-data pipelines, data warehousing, and modern data infrastructure. Data pipelines are the frameworks that enable raw data to flow from its source to its destination, often requiring multistage transformations, cleaning, and enrichment on the way. This process ensures that the data becomes usable and aligned with business goals. Afterwards, the refined data is sent for storage, usually to a data warehouse, where it gets collected in one place for querying and analysis. It also highlights that using modern infrastructure such as cloud storage and distributed computing can achieve great scale for data operations and can manage high volumes efficiently.


A key skill in working with data is the use of SQL, or Structured Query Language. SQL allows users to interact with relational databases, extracting information and manipulating data in everything from simple retrievals to complex joins and aggregations. The ability to build and optimize data queries, which are foundational to analyzing and interpreting large datasets, requires mastery in SQL. This chapter proceeds hands-on with SQL to take one through exercises that draw out the practical skills in querying databases. With the ever-increasing reliance on data-driven decision-making in organizations, good use of SQL becomes an essential tool in both the data analyst's and data engineer's toolkit.




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