What SQL operation would you use to retrieve data from one table that is not in another table?

• A. UNION
• B. MINUS
• C. JOIN
• D. CROSS JOIN

Answer: (B)

To retrieve data from one table that does not exist in another table, the MINUS operation is specifically designed to achieve this in SQL. When you use the MINUS operation, it compares the results of two SELECT statements and returns only the rows from the first SELECT statement that do not appear in the second SELECT statement.

This is particularly useful for finding discrepancies between datasets or isolating unique records from one table by excluding those that are present in another. For example, if you have a list of all employees in one table and a list of employees who are no longer with the company in another table, applying the MINUS operation would yield a list of current employees who are not in the termination list.

The other choices, while they involve data retrieval in SQL, do not serve the purpose of filtering out rows from one dataset based on non-existence in another. UNION combines results and removes duplicates across the two datasets, JOIN is used to combine rows from two or more tables based on a related column, and CROSS JOIN produces a Cartesian product of the two tables, which can yield an extensive number of results that would not address the specific need to exclude records.