Combining data
Data can be combined from multiple queries or even multiple source files depending on the nature of the data connected in the data model.
Power Query uses different terminology compared to technologies such as relational databases, so it's important to understand both the concepts as well as the terminology used for the PL-300 exam.
Using merge queries
Merge queries are used when we want to merge or combine columns from multiple queries where some columns are different. This often happens in data warehouse environments as data tends to be normalized or split across multiple tables (imported into a Power BI data model as a query). For more information on why data is normalized in a data warehouse, we recommend reading The Data Warehouse Toolkit: The Definitive Guide to Dimensional Modeling by Ralph Kimball. Tables contain key columns that allow individual records to be merged or joined together when needed. Normalizing data is standard practice for properly...