Question

A union query is which of the following? group of answer choices a. combines the output from multiple queries and does not include the same number of columns. b. combines the output from no more than two queries and does not include the same number of columns. c. combines the output from no more than two queries and must include the same number of columns.

d. combines the output from multiple queries and must include the same number of columns.

Answer 1

The correct answer is:

d. combines the output from multiple queries and must include the same number of columns.

Step-by-step explanation:

A union query is used to combine the results of two or more SELECT statements into a single result set. In a union query, the output from each SELECT statement must have the same number of columns, and the columns must have compatible data types.

For example, if we have two tables customers and suppliers, and we want to retrieve a list of all the names from both tables, we can use a union query like this:

SELECT name FROM customers

SELECT name FROM customersUNION

SELECT name FROM customersUNIONSELECT name FROM suppliers;

This query will combine the results of the two SELECT statements into a single result set, and will only return distinct values. Note that both SELECT statements in this query have the same number of columns (1), and the name column has the same data type in both tables.