Assume you are using the UNION operator to combine the results from two tables with identical structure,CUSTOMER and CUSTOMER_2.The CUSTOMER table contains 10 rows,while the CUSTOMER_2 table contains 7 rows.Customers Dunne and Olowski are included in the CUSTOMER table as well as in the CUSTOMER_2 table.How many records are returned when using the UNION operator?
A) 7
B) 10
C) 15
D) 17

Question

Quizplus · Accepted Answer

The UNION operator takes the distinct rows from both tables and combines them into a single result set. Since the two tables have identical structures, including the columns and data types, the resulting combined table will also have the same structure. Therefore, the total number of rows returned will be the sum of the number of rows in CUSTOMER and CUSTOMER_2, minus any duplicates.

In this case, there are 10 rows in CUSTOMER and 7 rows in CUSTOMER_2, for a total of 17 rows. However, since the customers Dunne and Olowski appear in both tables, they will be included only once in the result set, so the final number of distinct rows will be 15. Therefore, the correct answer is C.

Assume You Are Using the UNION Operator to Combine the Results