[Solved] You have a table products with an index on price. You run this query:UPDATE products SET price = price * 1.1; but it runs very slowly. What is the most likely cause? | SQL

SQL - Indexes and Query Performance

You have a table products with an index on price. You run this query:

UPDATE products SET price = price * 1.1;

but it runs very slowly. What is the most likely cause?

AThe index on <code>price</code> must be updated for every row, slowing the update.

BThe query syntax is incorrect and causes a full table scan.

CThe index on <code>price</code> speeds up the update, so slowness is unrelated.

DThe database ignores indexes on UPDATE, so the index has no effect.

Step-by-Step Solution

Solution:

Step 1: Recognize that updating an indexed column affects the index
Since price is indexed and updated for every row, the index must be updated repeatedly.
Step 2: Understand the performance impact
Updating the index for many rows causes significant overhead, slowing the query.
Final Answer:
The index on price must be updated for every row, slowing the update. -> Option A
Quick Check:
Index update overhead = slow UPDATE [OK]

Quick Trick: Mass updates on indexed columns slow queries due to index updates [OK]

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