What does a transformation using a left join imply about dataset size?

A transformation using a left join can indeed result in an increase in dataset size due to the nature of how left joins operate. When a left join is performed, all records from the left dataset are included in the results, along with corresponding matches from the right dataset. If there are multiple matches for a single record in the right dataset, then the result will include several new rows, one for each match. This can lead to an overall increase in the number of rows in the resulting dataset compared to the left dataset alone.

For instance, if the left table contains unique identifiers and the right table has multiple associated records for those identifiers, then each unique identifier from the left will result in multiple rows in the output, thus expanding the dataset size. Therefore, it is accurate to say that a left join may increase the total number of rows in the merged dataset due to the potential for multiple matches from the right table.