Question

Compared to a DIFFERENCE, a LEFT OUTER JOIN may:

Include:
a) Only common elements
b) All elements from the left table
c) All elements from the right table
d) Elements that are different

Answer 1

A LEFT OUTER JOIN includes all elements from the left table and the matched elements from the right table differing from a DIFFERENCE which includes elements only in the first set but not the second.

Step-by-step explanation:

When compared to a DIFFERENCE a LEFT OUTER JOIN in SQL includes: b) All elements from the left table along with matched elements from the right table. In contrast a DIFFERENCE operation (such as the EXCEPT clause in SQL) would only include elements that are present in the first set (or table) but not in the second.

So a LEFT OUTER JOIN will return all the records from the left table as well as the matched records from the right table if available if there is no match NULL values are filled in for the right table's columns.