What is 'xyz' in the following SQL statement?

SELECT xyz FROM table1 UNION xyz FROM table2;

This question is asking about the meaning of the word "xyz" in the given SQL statement.

The statement uses the UNION operator, which combines the results of two SELECT queries.

In the first query, "SELECT xyz FROM table1", "xyz" is what we are selecting. This means "xyz" must be a name that identifies something within the table.

The options are:
* Option A: row name - Rows are not named in SQL.
* Option B: column name - This is the most likely answer. Columns are named and hold specific data within a table.
* Option C: table name - Table names are used to specify which table to use in the query, and are not used within the SELECT statement.
* Option D: database name - Database names are used to specify which database the tables are in, and are not used within the SELECT statement.

Therefore, the correct answer is Option B: column name.