Final answer:
A non-equality join refers to a SQL join where the join predicate is not based on equality, but instead on other comparison operators.
Step-by-step explanation:
A non-equality join does not mean a table is joined to itself; rather, it is a type of join where the join condition is based on something other than equality (!=, <, <=, >, >=). In SQL, this type of join is typically used to compare columns for greater than or less than relationships. For example, if you want to join two tables based on an employee’s salary being higher than a certain threshold, you'd use a non-equality join.
Joining a table to itself, on the other hand, is known as a self join. A self join can be an equality join or a non-equality join, depending on the conditions you set out for the join. A self join is when a table is joined to itself, and it can be either an equality or non-equality join.