Which process is involved in creating composite keys in ETL?

Creating composite keys is primarily a function of the Transform phase in the ETL (Extract, Transform, Load) process. During the Transform phase, data undergoes various operations like cleaning, aggregating, and reformatting to prepare it for analysis. A composite key is formed when two or more fields are combined to create a unique identifier for records in a dataset.

In this context, the main purpose of using composite keys is to ensure the uniqueness of records, which is vital when consolidating data from multiple sources that may have overlapping or similar values. By creating composite keys during the Transform phase, you can effectively handle scenarios such as merging tables or managing relationships between them. This ensures that the dataset maintains its integrity and that each record can be uniquely identified in downstream processes.

The other phases—Extract, Load, and Data preparation—do not primarily focus on the creation of composite keys. The Extract phase is about pulling data from various sources, the Load phase involves storing the transformed data into a target system, and the Data preparation phase is typically broader than just key creation, often involving initial cleaning and shaping of data before deeper transformations occur.