Comprehensive and Detailed In-Depth Explanation:
In SQL, different types of joins are used to combine records from two or more tables based on related columns. The choice of join affects the result set, especially concerning the inclusion of duplicates and the completeness of data retrieval.
* FULL OUTER JOIN: Retrieves all records when there is a match in either left or right table. Non- matching rows will also be included, with NULLs in place where the join condition is not met.
* INNER JOIN: Retrieves only the records that have matching values in both tables.
* LEFT OUTER JOIN: Retrieves all records from the left table and the matched records from the right table. Non-matching rows from the right table will result in NULLs.
* CROSS JOIN: Returns the Cartesian product of the two tables, meaning it combines all rows from the first table with all rows from the second table. This join includes all possible combinations, resulting in a dataset that contains all records from both tables, including duplicates.
Given the requirement to return all records from several tables, even duplicates, a CROSS JOIN is appropriate. However, it's essential to note that a CROSS JOIN can produce a very large result set, especially if the tables have many rows. Therefore, it should be used cautiously and typically with additional filtering to manage the size of the output.