Question

UNION by default removes duplicates. SELECT 1, 'a' UNION SELECT 1, 'a' UNION SELECT 2, 'b' Will only have 1 a and 2 b

Option 1: UNION
Option 2: INTERSECT
Option 3: EXCEPT
Option 4: JOIN

Answer 1

The question involves the SQL set operator UNION, which removes duplicates, contrasting with the behaviors of INTERSECT, EXCEPT, and JOIN.

Step-by-step explanation:

The student's question pertains to the behavior of different SQL set operators when used in database queries. In the given case, using UNION will indeed result in a distinct set of rows, hence the output will contain only one occurrence of '1, a' and one occurrence of '2, b'. UNION by default removes duplicates, ensuring that each row of the result is unique. On the other hand, INTERSECT returns only the rows that are common to both queries, while EXCEPT returns only the rows from the first query that are not present in the output of the second query. Lastly, JOIN is used to combine rows from two or more tables based on a related column between them.