Understanding the functionality of SQL joins and their application in a relational database:

Option A: Correct. A self join is used to relate or compare rows within the same table. It typically involves using table aliases to distinguish the different instances of the table in the query.

Option B: Incorrect. An inner join relates rows between two different tables based on a common condition, not within the same table.

Option C: Incorrect. SQL allows joining of rows from any tables, whether directly related by foreign keys or not, as long as there is a logical condition that can relate their columns.

Option D: Correct. Sometimes establishing a relationship between two specific tables might require joining through one or more intermediary tables, particularly in cases involving complex relationships or normalization.

Option E: Incorrect. While joins are often used to implement relationships, not every logical relationship necessitates a join condition, especially if data from only one table is required or if multiple relations are possible but not relevant to the specific query.