A developer created an index but the database shows it is not being used. What is a common mistake causing this?

medium📝 Debug Q7 of 15

SQL - Indexes and Query Performance

AThe index name is too long and ignored by the database.

BThe index was created on a different table than queried.

CThe database automatically disables all indexes after creation.

DThe query uses functions on the indexed column, preventing index use.

Step-by-Step Solution

Solution:

Step 1: Understand index usage restrictions
Using functions on indexed columns can prevent the database from using the index.
Step 2: Analyze options
The query uses functions on the indexed column, preventing index use. correctly identifies a common cause; others are false or unlikely.
Final Answer:
The query uses functions on the indexed column, preventing index use. -> Option D
Quick Check:
Functions on indexed columns block index use [OK]

Quick Trick: Avoid functions on indexed columns to use indexes [OK]

Common Mistakes:

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