For SQL queries involving set operations like UNION, UNION ALL, INTERSECT, and MINUS, the data types and number of columns in the SELECT statements being combined must be the same. Here is a breakdown of each query option:
* Option A: This query successfully combines results from two tables using UNION ALL, which combines all rows from both SELECT statements, including duplicates. Both queries select two columns (prod_id and exp_date, with exp_date being NULL in the second query). This is valid as the number of columns and their data types match.
* Option B: This query attempts to use INTERSECT, which returns only the rows common to both SELECT statements. However, the first SELECT statement chooses prod_id and prod_name, while the second only substitutes a constant value for prod_id without specifying from which table it selects prod_name. If "newproducts" (presumably a typo and should be "new_products") does not have the exact columns as "products", or if the data types do not match, it will fail.
* Option C: This query uses UNION, which removes duplicates from the combined dataset. The use of SELECT * assumes that both "products" and "new_products" tables have the same columns in the same order with matching data types. This query will succeed if those conditions are met.
* Option D: This query uses MINUS to subtract results of the second SELECT from the first. However, it fails because 'k' does not explicitly match a column name in "products", suggesting a potential error unless 'k' is indeed a valid column.
* Option E: This query fails because the first SELECT statement fetches only one column (prod_id) while the second fetches two columns (prod_id and prod_name). UNION ALL requires the same number of columns with compatible types in all SELECT statements involved.