What problems can arise when using the JOIN operator…

Cartesian Product (Cross Join): Occurs when there is no ON or USING condition, or it is incorrect, leading to a combination of each row from one table with every row from the other.
Data duplication: An incorrect JOIN can result in multiple displays of the same rows if one table has several matching records in the other.
Performance:
- Lack of indexes on the fields used for JOIN.
- JOIN on inefficient data types (e.g., TEXT or BLOB).
- A large number of tables in a single JOIN.
- Using functions in ON conditions.
Unexpected NULL values: When using LEFT JOIN or RIGHT JOIN, if there are no matching records in the join table, the fields from that table will contain NULL. FULL OUTER JOIN can lead to NULL on both sides.
Incorrect JOIN type: Choosing the wrong JOIN type (INNER, LEFT, RIGHT, FULL OUTER) can result in errors or include unwanted data in the result.
Errors in JOIN conditions: Incorrect conditions in ON or USING can lead to incorrect results or missing expected data.
Query complexity: JOIN of many tables makes SQL queries hard to read and debug.

What problems can arise when using the JOIN operator in SQL?