Performance fact of using multiple loops(not nested) / single loop for the same dataset

For exporting data as pdf, i need to query a dataset from the database and then loop through it to manage indexes and then export as pdf. When querying, the dataset can be manipulated in different ways with the use of joins and other mechanism. The confusion is, depending on the structure of the dataset, it can be done within a single loop and it may be done with multiple loops(not nested). What is the performance effect of these two ways.

For example: dataset contains "organizations" and its "inquries"."inquiries" has different types. In this condition, I can query to retrieve dataset as whole and use one loop to go through it or retrieve dataset as sections and then use multiple loops to go through.

What is the performance fact of these two scenarios. Thanks in advance