[Solved] A B-tree index was created on column age, but a query with WHERE age + 1 = 30 is slow. Why? — Ans: The expression prevents the index from being used. | SQL

SQL - Indexes and Query Performance

A B-tree index was created on column age, but a query with WHERE age + 1 = 30 is slow. Why?

AThe database ignores indexes on numeric columns.

BThe expression prevents the index from being used.

CThe query syntax is invalid.

DThe index is corrupted and needs rebuilding.

Step-by-Step Solution

Solution:

Step 1: Understand index usage with expressions
Using arithmetic expressions on indexed columns disables index usage.
Step 2: Check other options
No evidence of corruption; query syntax is valid; numeric columns support indexes.
Final Answer:
The expression prevents the index from being used. -> Option B
Quick Check:
Expressions on indexed columns block index use [OK]

Quick Trick: Avoid expressions on indexed columns to keep index use [OK]

Common Mistakes:

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A B-tree index was created on column age, but a query with WHERE age + 1 = 30 is slow. Why?