[Solved] What restriction does the UNIQUE constraint impose on a column in a SQL table? — Ans: It prevents duplicate values in that column. | SQL

SQL - Table Constraints

What restriction does the UNIQUE constraint impose on a column in a SQL table?

AIt automatically indexes the column as a primary key.

BIt allows only NULL values in that column.

CIt prevents duplicate values in that column.

DIt restricts the column to numeric values only.

Step-by-Step Solution

Solution:

Step 1: Understand UNIQUE constraint
The UNIQUE constraint ensures that all values in a column are distinct.
Step 2: Analyze options
It prevents duplicate values in that column. correctly states this. It allows only NULL values in that column. is incorrect because UNIQUE allows multiple NULLs in many DBMS. It automatically indexes the column as a primary key. is wrong because UNIQUE is not the same as PRIMARY KEY. It restricts the column to numeric values only. is unrelated.
Final Answer:
It prevents duplicate values in that column. -> Option C
Quick Check:
UNIQUE means no duplicates allowed [OK]

Quick Trick: UNIQUE means no duplicate values allowed [OK]

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What restriction does the UNIQUE constraint impose on a column in a SQL table?