GROUP BY Options in Azure Synapse Dedicated SQL Pool
Question
Peter is a Data Engineer for Adatum Corporation.
He is working on implementing tables on dedicatedSQL pools of Azure Synapse with T-SQL queries.
He needs to use the GROUP BY clause for aggregating data to a summary set of rows.
Which of the following three GROUP BY options are supported in the dedicated SQL pool of Azure Synapse?
Answers
Explanations
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A. B. C. D. E.Correct Answers: B, D and E
Serverless SQL pool doesn't support the GROUP BY options.
The Dedicated SQL pool has limited options for supporting GROUP BY clause.
Option A is incorrect because there's no such option for GROUP BY clause in a dedicated SQL pool as GROUP BY with hashing.
Option B is correct because with the UNION ALL the Rollup can be executed for GROUP BY rather than explicit usage of syntax.
For example: the following GROUP BY Statement can be executed with the ROLLUP option.
Azure Synapse Analytics is an integrated analytics service that allows data engineers and data scientists to prepare, manage, and analyze data using T-SQL queries, Spark, and Power BI. Azure Synapse Analytics has dedicated SQL pools that enable data engineers to query large volumes of data using T-SQL queries.
When it comes to aggregating data to a summary set of rows, the GROUP BY clause is one of the most important features in T-SQL queries. It enables data engineers to group rows based on a specific column or a combination of columns, and then apply aggregate functions to each group to compute summary statistics.
The following are the GROUP BY options that are supported in the dedicated SQL pool of Azure Synapse:
GROUP BY with Hashing: This option is used to hash the grouping column(s) and distribute the rows among the compute nodes in a round-robin fashion. This option is ideal for distributing the workload evenly across the nodes and achieving high query performance.
GROUP BY with ROLLUP: This option is used to generate subtotals and grand totals for a group of columns. It creates additional rows to represent the subtotals and grand totals based on the hierarchy of the columns specified in the GROUP BY clause.
GROUP BY with GROUPING SETS: This option is used to group data by multiple sets of columns, each of which can be aggregated using different aggregate functions. It generates a result set that includes all the grouping sets, including the individual columns, all possible combinations of columns, and the grand total.
GROUP BY with CUBE: This option is used to generate all possible combinations of the columns specified in the GROUP BY clause. It generates a result set that includes the subtotals and grand totals for each combination of columns.
Therefore, the correct answers to the question are:
- GROUP BY with Hashing
- GROUP BY with ROLLUP
- GROUP BY with GROUPING SETS
- GROUP BY with CUBE
