Home » Microsoft » DP-203 » Which table distribution will minimize query times?
You are designing a fact table named FactPurchase in an Azure Synapse Analytics dedicated SQL pool. The table contains purchases from suppliers for a retail store. FactPurchase will contain the following columns.
FactPurchase will have 1 million rows of data added daily and will contain three years of data.
Transact-SQL queries similar to the following query will be executed daily.
SELECT
SupplierKey, StockItemKey, IsOrderFinalized, COUNT(*)
FROM FactPurchase
WHERE DateKey >= 20210101
AND DateKey <= 20210131
GROUP By SupplierKey, StockItemKey, IsOrderFinalized
Which table distribution will minimize query times?
A. replicated
B. hash-distributed on PurchaseKey
C. round-robin
D. hash-distributed on IsOrderFinalized
Correct Answer: B
Explanation/Reference:
Hash-distributed tables improve query performance on large fact tables.
To balance the parallel processing, select a distribution column that:
Has many unique values. The column can have duplicate values. All rows with the same value are assigned to the same distribution. Since there are 60 distributions, some distributions can have > 1 unique values while others may end with zero values.
Does not have NULLs, or has only a few NULLs. Is not a date column.
Incorrect Answers:
C: Round-robin tables are useful for improving loading speed.
Reference:
https://docs.microsoft.com/en-us/azure/synapse-analytics/sql-data-warehouse/sql-data-warehouse-tables-distribute
