Data Quality Patterns — Identifying the Multivalue, Multicolumn Problem Each option shows example table data. Which option demonstrates the multivalue, multicolumn anti-pattern (storing multiple values across several columns in the same row)?
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AThree columns have the values 534-2435, 534-7867, and 546-2356 in the same row.
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BThree rows have the values Brown Small Chair, Small Chair Brown, and Small Brown Chair in the same column.
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CThree rows have the values Brown, NULL, and Blue in the same column.
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DOne row has the value 'He is interested in a Silver Porsche from the years 1978-1988' in a column.
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EA single column stores a JSON array of phone numbers as text.
Answer
Correct Answer: Three columns have the values 534-2435, 534-7867, and 546-2356 in the same row.
Explanation
Introduction:The multivalue, multicolumn problem arises when multiple values of the same attribute are stored across several columns in a single row (for example, Phone1, Phone2, Phone3). This breaks first normal form (1NF) and complicates querying, indexing, and constraint enforcement. The question asks you to identify this anti-pattern from sample data.
Given Data / Assumptions:
- We are evaluating examples purely for modeling quality.
- 1NF requires atomic values in each column and a fixed number of columns per attribute.
- Phone numbers repeated across columns are a classic symptom.
Concept / Approach:Compare each example with the 1NF rule. If multiple values of the same attribute appear as separate columns in a single row, the design is violating 1NF and causing maintenance headaches (for example, searching all phone columns, or exceeding a fixed maximum number).
Step-by-Step Solution:1) Inspect (a): multiple phone numbers in separate columns within one row → multivalue, multicolumn.2) Inspect (b): same tokens in different orders → inconsistent values, not multicolumn.3) Inspect (c): presence of NULL → missing values issue.4) Inspect (d): long free-text → general-purpose remarks problem.5) Therefore, (a) is the correct example.
Verification / Alternative check:Normalized modeling would create a separate related table (for example, CustomerPhone with CustomerID and PhoneNumber), storing one phone per row.
Why Other Options Are Wrong:
- (b) Inconsistent values: Token order inconsistency, not multiple columns.
- (c) Missing values: NULL indicates absence, not multicolumn.
- (d) Remarks column: Free-text mixture of concepts, not multicolumn.
- (e) JSON array: Multivalue single column (violates 1NF) but not the asked “multicolumn” pattern.
Common Pitfalls:Confusing multivalue-in-one-column (also a 1NF violation) with multivalue-across-columns. The question specifically targets the multicolumn manifestation.
Final Answer:Three columns have the values 534-2435, 534-7867, and 546-2356 in the same row.