Union, intersection, difference in DBMS Theory - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the UNION operation in set theory or databases?

UNION combines all unique elements from two sets or tables, removing duplicates to form a single set.

beginner

Define INTERSECTION in the context of databases.

INTERSECTION returns only the elements that appear in both sets or tables.

beginner

What does the DIFFERENCE operation do?

DIFFERENCE returns elements that are in the first set but not in the second set.

intermediate

How does UNION handle duplicate records in database tables?

UNION removes duplicate records, so each record appears only once in the result.

intermediate

Can INTERSECTION be used to find common customers in two sales tables?

Yes, INTERSECTION returns customers present in both sales tables, showing common entries.

Which operation returns all unique records from two tables combined?

A INTERSECTION

B UNION

C DIFFERENCE

D JOIN

UNION combines all unique records from both tables, removing duplicates.

What does INTERSECTION return when applied to two sets?

A Elements only in the first set

B Elements only in the second set

C Elements common to both sets

D All elements from both sets

INTERSECTION returns only the elements that appear in both sets.

If you want to find records in Table A but not in Table B, which operation do you use?

A UNION

B INTERSECTION

C CROSS JOIN

D DIFFERENCE

DIFFERENCE returns records in the first set (Table A) that are not in the second (Table B).

Does UNION include duplicate records in the result?

A No, duplicates are removed

B Yes, all duplicates are included

C Only duplicates from the first set are included

D Only duplicates from the second set are included

UNION removes duplicates so each record appears only once.

Which operation would you use to find customers who bought products from both Store A and Store B?

A INTERSECTION

B UNION

C DIFFERENCE

D FULL OUTER JOIN

INTERSECTION finds common customers present in both Store A and Store B.

Explain the difference between UNION, INTERSECTION, and DIFFERENCE operations with examples.

Think about combining lists, finding common friends, or removing items.

How can UNION, INTERSECTION, and DIFFERENCE be useful in managing data in databases?

Consider scenarios like combining customer lists or comparing inventories.