Question

In the context of DBMS, consider the two sets T and S given below.

T	S
I: Logical schema	L: Views
II: Physical schema	M: File organization and indexes
III: External schema	N: Relations

Which one of the following is the correct match from T to S?

• A. I - L, II - M, III - N
• B. I - M, II - L, III - N
• C. I - N, II - M, III - L
• D. I - N, II - L, III - M

Hint:

Logical schema holds the relations, physical schema is about file organization and indexes, and external schema is implemented as views.

Answer 1

The Correct Option is C

Step 1: Recall the three-schema (ANSI-SPARC) architecture of a DBMS.
A DBMS is organized into three levels of schema. The Logical schema (also called the conceptual schema) describes the overall structure of the whole database for the community of users, in terms of what data is stored and the relationships between them, this is where the actual relations (tables) of a relational database are defined. The Physical schema describes how the data is actually stored on physical storage media, including file organization and the indexes built for fast access. The External schema describes a specific user's or application's partial view of the database, and is implemented through views.

Step 2: Match each item in T to its description in S.
I: Logical schema describes the database's overall conceptual structure, which is exactly where the Relations (tables) of the database are defined, so I - N. II: Physical schema is exactly about how data sits on disk, which is File organization and indexes, so II - M. III: External schema is exactly the user-specific partial view mechanism, which is implemented as Views, so III - L.

Step 3: Combine the matches.
I - N, II - M, III - L is exactly option (C).

Step 4: Why the other options are wrong.
Option (A), I - L, II - M, III - N, wrongly pairs Logical schema with Views (that pairing actually belongs to External schema) and External schema with Relations (that pairing actually belongs to Logical schema), swapping I and III. Option (B), I - M, II - L, III - N, incorrectly claims the Logical schema is about file organization and indexes (that is the Physical schema's job) and the Physical schema is about views (that is the External schema's job). Option (D), I - N, II - L, III - M, keeps I correct but swaps Physical and External, claiming Physical schema is implemented as views and External schema is about file organization and indexes, which is backwards, views are a purely logical/user-facing concept with no direct connection to physical storage.

Final Answer:
Logical schema matches Relations, Physical schema matches File organization and indexes, and External schema matches Views.
\[ \boxed{\text{I - N, II - M, III - L (option C)}} \]