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The Microsoft Azure SQL Solutions exam (Exam DP-300) assesses your skills in administering Microsoft Azure SQL databases. One important aspect of administering SQL solutions is optimizing resource usage. In this article, we will explore various query construct modifications that can help improve resource usage in Azure SQL.
Indexes improve query performance by reducing the number of I/O operations required to retrieve data. Be sure to create appropriate indexes on frequently queried columns and optimize existing indexes to suit your workload.
Instead of selecting all columns using “SELECT *”, specify only the required columns. This reduces the amount of data transferred over the network and improves query execution time.
Each join operation adds complexity and can have a negative impact on query performance. Minimize the number of joins by denormalizing tables or using appropriate indexing strategies.
When checking the existence of records, use the EXISTS operator instead of counting the number of records. EXISTS stops processing as soon as it finds a match, whereas COUNT scans all records.
-- Use EXISTS instead of COUNT
IF EXISTS (SELECT 1 FROM Table WHERE Condition)
BEGIN
-- Do something if records exist
END
Use the TOP clause or OFFSET-FETCH clause to limit the number of rows returned by a query. This reduces resource consumption and improves query performance.
-- Use TOP to limit result set
SELECT TOP (10) Column1, Column2
FROM Table
When combining results of multiple queries, use UNION ALL instead of UNION. UNION removes duplicate rows, which requires additional processing time and resources.
Subqueries often impact performance. If possible, rewrite subqueries as JOIN statements to improve query execution time.
When querying large datasets multiple times, consider storing interim results in temporary tables or table variables. This reduces redundant calculations and improves performance.
-- Create a temporary table
CREATE TABLE #TempTable
(
Column1 datatype1,
Column2 datatype2
)
-- Insert data into temp table
INSERT INTO #TempTable (Column1, Column2)
SELECT Column1, Column2
FROM Table
-- Use temp table in subsequent queries
SELECT *
FROM #TempTable
If a subquery is used to filter rows, avoid using ORDER BY within the subquery. Sorting adds overhead and may not affect the final result.
Regularly monitor query performance using tools like Azure SQL Database Query Performance Insight. Identify expensive queries and optimize them to improve overall resource usage.
By implementing these query construct modifications, you can optimize resource usage in your Azure SQL solutions. Remember to test and adapt these modifications to match your specific workload and requirements.
a) It increases the number of query plans stored per query in the Query Store.
b) It decreases the number of query plans stored per query in the Query Store.
c) It has no impact on the number of query plans stored per query in the Query Store.
d) It removes all existing query plans stored per query in the Query Store.
Correct answer: a) It increases the number of query plans stored per query in the Query Store.
Correct answer: True
a) It allows for higher resource usage and performance.
b) It reduces resource usage and performance.
c) It has no impact on resource usage and performance.
d) It stops all resource usage and performance.
Correct answer: a) It allows for higher resource usage and performance.
Correct answer: True
a) It increases the degree of parallelism used for query execution.
b) It decreases the degree of parallelism used for query execution.
c) It has no impact on the degree of parallelism used for query execution.
d) It stops all query execution.
Correct answer: a) It increases the degree of parallelism used for query execution.
Correct answer: True
a) It automatically identifies and creates missing indexes for improved query performance.
b) It disables indexing for all queries.
c) It removes all existing indexes for improved query performance.
d) It has no impact on query performance.
Correct answer: a) It automatically identifies and creates missing indexes for improved query performance.
Correct answer: True
a) It improves query performance and reduces resource usage.
b) It decreases query performance and increases resource usage.
c) It has no impact on query performance and resource usage.
d) It stops all query processing.
Correct answer: a) It improves query performance and reduces resource usage.
Correct answer: True
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