What happens when you select a left join in data transformation?

Selecting a left join in data transformation means that you will retain all entries from the left dataset while also including any matching entries from the right dataset. When there is no match for a left dataset entry in the right dataset, the result will display null values for the right dataset's fields corresponding to that entry. This join type effectively combines these two datasets, ensuring that every entry from the left dataset is represented in the final output, which aligns with the true purpose of a left join.

New rows are not specifically created for every match in the right dataset, but rather, existing rows from the left dataset are preserved, and only those entries in the right dataset that correspond to matches are included. Hence, the notion of retaining all left dataset rows while seeking matches from the right is central to understanding how a left join functions in relational databases.