Which SQL command did the database administrator use to combine potential and actual customer data?

• A. JOIN
• B. UNION
• C. SELECT
• D. MERGE

Answer: (B)

The command used to combine potential and actual customer data in SQL is UNION. This command is specifically designed to combine the results of two or more SELECT queries into a single result set. It takes the output of multiple SELECT statements and adds them together, ensuring that the result contains a unique set of records.

In the context of combining potential and actual customer data, using UNION is appropriate because the two sets of data may contain similar columns but come from different tables or queries. UNION effectively allows the administrator to create a unified dataset that summarizes all relevant customer information, ensuring that there are no duplicates in the final output if the same customer appears in both groups.

While JOIN can also combine data from different tables, it does so based on common keys or relationships, which is more oriented toward merging records that have matching fields. SELECT is a basic command used to specify which columns of data to retrieve without merging datasets. MERGE, often used in data manipulation, serves a different purpose, typically for inserting or updating records but is not primarily used for combining datasets in the manner implied in this question.

Therefore, the most appropriate command for the scenario described is UNION, which serves the function of consolidating varying data into a cohesive whole.