The UNION ALL operator in SQL combines the results of two or more SELECT statements into a single result set:
Option A: True. Since UNION ALL does not eliminate duplicates, it does not ignore NULLs during any duplicate checking; however, it's worth noting that UNION ALL does not perform duplicate checking at all.
Option B: False. Unlike the UNION operator, UNION ALL does not eliminate duplicates; it includes all duplicates in the output.
Option C: False. The column names do not need to be identical in each SELECT statement; however, the result set will use the column names from the first SELECT statement.
Option D: True. For UNION ALL to work correctly, the number of columns and their data types in each SELECT statement must match, but the column names can differ.
Option E: False. UNION ALL does not inherently sort the output; it merely combines the results as they are retrieved. Any sorting would need to be explicitly specified using an ORDER BY clause.