[Solved] Consider a table employees with an index on department_id. What is the effect of this UPDATE statement?UPDATE employees SET department_id = 5 WHERE employee_id = 10; | SQL

SQL - Indexes and Query Performance

Consider a table employees with an index on department_id. What is the effect of this UPDATE statement?

UPDATE employees SET department_id = 5 WHERE employee_id = 10;

AThe update is faster because the index helps locate the row.

BThe update fails because indexed columns cannot be changed.

CThe update is slower because the index on <code>department_id</code> must be updated.

DThe update runs at normal speed ignoring the index.

Step-by-Step Solution

Solution:

Step 1: Identify the column being updated and its index
The column department_id is indexed and is being updated.
Step 2: Understand index maintenance on UPDATE
Updating an indexed column requires updating the index, which adds overhead and slows the operation.
Final Answer:
The update is slower because the index on department_id must be updated. -> Option C
Quick Check:
Index update overhead = slower UPDATE [OK]

Quick Trick: Updating indexed columns slows UPDATE due to index changes [OK]

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