[Solved] You have a denormalized table where customer phone numbers are repeated in many rows. You run this update:... What is the most likely problem? | SQL

SQL - Database Design and Normalization

You have a denormalized table where customer phone numbers are repeated in many rows. You run this update:

UPDATE Orders SET CustomerPhone = '123-4567' WHERE CustomerID = 5;

but some rows still show old phone numbers. What is the most likely problem?

AThe WHERE clause did not match all rows for CustomerID 5

BDenormalization prevents updates to repeated data

CCustomerPhone is a computed column and cannot be updated

DThe database automatically updates all rows, so this is impossible

Step-by-Step Solution

Solution:

Step 1: Analyze update query symptom and identify cause
The update targets rows with CustomerID = 5, but some rows still have old data, meaning some rows were missed. Most likely, some rows have incorrect or missing CustomerID values, so the WHERE clause did not match them.
Final Answer:
The WHERE clause did not match all rows for CustomerID 5 -> Option A
Quick Check:
Update misses rows if WHERE condition is incomplete [OK]

Quick Trick: Check WHERE clause matches all repeated rows in denormalized tables [OK]

Common Mistakes:

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