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: Instead of matching definitions one by one, order the three schema levels by how close they sit to the physical disk versus how close they sit to an individual user, and match S in the same order.

Step 2: The level closest to the disk is the Physical schema, since it is only concerned with the mechanics of storage, how records are laid out in files and which indexes exist to speed up lookups. Among the S options, "File organization and indexes" (M) is the only one describing storage mechanics, so Physical schema (II) pairs with M.

Step 3: The level closest to an individual user or application is the External schema, since different users can be given different, restricted, or customized views of the same underlying data without touching the real tables. Among the S options, "Views" (L) is the only user-facing, customizable presentation mechanism, so External schema (III) pairs with L.

Step 4: That leaves the middle level, the Logical schema, which describes the database as a whole for the entire user community, independent of both physical storage details and any single user's restricted viewpoint. This is exactly where the actual base tables, the Relations (N), of the database live, so Logical schema (I) pairs with N.

Step 5: This ordering-based reasoning, physical to storage mechanics, external to user views, logical to the base relations in between, gives I - N, II - M, III - L, which is option (C), the same result direct definition matching confirms.

\[ \boxed{\text{I - N, II - M, III - L (option C)}} \]