In a proper relation, does the order of the columns (attributes) matter for the meaning of the data?

Difficulty: Easy

Correct Answer: Correct

Explanation:

Introduction / Context:Attributes in a relation form a set, and sets have no inherent order. This question checks whether column order is semantically meaningful in the relational model.

Given Data / Assumptions:

  • A relation is defined over a set of attributes, not an ordered list.
  • SQL may display columns in a chosen order, but that is presentation.
  • Users can request any explicit order in SELECT lists.

Concept / Approach:Because attributes are a set, shuffling column positions does not change the relation’s meaning. Only attribute names and their domains matter. Any dependence on visual position is a UI concern, not a relational one.

Step-by-Step Solution:

Recall set semantics: sets are unordered.Relate to schema: schema defines attribute names and types, not positions.Conclude: column order does not matter to the relation’s semantics; thus the statement is correct.

Verification / Alternative check:Write SELECT y, x FROM T; it is the same data as SELECT x, y FROM T reordered; the schema is unchanged.

Why Other Options Are Wrong:

  • “Incorrect” conflicts with fundamental set semantics.
  • Mentions of SELECT * or composite keys are implementation/presentation issues, not changes to meaning.

Common Pitfalls:Believing that position in CREATE TABLE determines semantics. It determines default display order only.

Final Answer:Correct

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