DP-203 Design and implement data storage Practice Question
Your company uses Azure Synapse Analytics dedicated SQL pool for a data warehouse. You notice that queries on a large fact table are slow. The table is hash-distributed on CustomerID and has 60 distributions. After reviewing the query plan, you see that many queries filter on OrderDate. You want to improve query performance without redesigning the table. What should you do?
⚠ Common exam trap
Many exam-takers assume changing the distribution key (Option A) is the only way to optimize filter-heavy queries, but they overlook that a clustered columnstore index with ORDER BY can provide similar I/O reduction without the risks of data skew or redesign.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a clustered columnstore index on the table and order by OrderDate
Creating a clustered columnstore index with ORDER BY OrderDate on the fact table improves query performance by physically ordering the data by OrderDate within each columnstore segment. This allows segment elimination during queries that filter on OrderDate, reducing the amount of data scanned. Since the table is already hash-distributed on CustomerID, this approach does not require redesigning the table and directly addresses the slow queries without changing the distribution strategy.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Change the distribution key to OrderDate
Why it's wrong here
Changing distribution key requires table redesign and may impact join performance.
- ✗
Recreate the table with round-robin distribution
Why it's wrong here
Round-robin distribution would hurt join performance on CustomerID.
- ✗
Update statistics only on the OrderDate column
Why it's wrong here
Statistics alone may not provide enough performance improvement without an appropriate index.
- ✓
Create a clustered columnstore index on the table and order by OrderDate
Why this is correct
Clustered columnstore index with ordering by OrderDate accelerates range queries.
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Senior Network & Security Engineer · founder of Courseiva
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