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SQL Server Performance Tuning

Performance monitoring includes monitoring the MS SQL Server database. MS SQL Server and the Microsoft Windows OS provide monitoring utilities to optimize the resources and improve performance.

System/Performance Monitor

This tool monitors the utilization of system resources.

Go to Start > Run, type perfmon and select OK.

Performance Monitor

To add/delete the key parameters, use the Add (green) and Delete (red) keys on the Performance Monitor screen.

Activity Monitor in SSMS

The Activity Monitor monitors the query execution and displays statistics such as Processes, Resource Waits, Recent and Active Expensive Queries.

  • Open SSMS, and connect to your server instance.
  • Select Activity Monitor from the top ribbon bar.

Activity Monitor

Performance Dashboard in SSMS

The dashboard provides visual insights into the performance of the SQL Server instance.

Right-click on the SQL Server instance name in the Object Explorer on the right. Then select Reports > Standard Reports > Performance Dashboard.

Performance Dashboard

The Performance Dashboard helps to identify System CPU Utilization, Current Waiting Requests, and performances measured based on the listed metrics.

Execution Plan - Estimated and Actual

The cost-based query optimizer in SQL Server calculates costs based on multiple possible plans. Click the Estimated Execution Plan and Actual Executed Plan button next to the Execute button in SSMS.

The actual execution plan includes runtime statistics. To capture an actual execution plan, you must execute the query.

In general, you can use the estimated execution plan to monitor the performance of your query. The actual execution plan determines the runtime performance of the query.

Estimated execution plan

In the actual execution plan, the Nested Loops component indicates a red cross.

Actual execution plan

When you hover over each component, you can view additional information.

Component info

To optimize this query, rewrite it as the first query with selected columns and a join clause.

Query Optimization

Here are some of the SQL query best practices that you may follow for better SQL Server database performance.

  • Instead of SELECT * query, use specific column names. Fetching all rows result in CPU, memory, I/O overhead and slows down performance. When you define the fields, the query optimizer queries only the required table data.
  • The DISTINCT query works by grouping all the fields in the query to create distinct rules. Such a grouping of fields consumes enormous processing power. Instead, mention additional and relevant column names in the SELECT query to yield unique results.
  • Use wildcards % sparingly and preferably at the end of the phrase (search text). A random wildcard broadens the search.
  • Use the WHERE clause to filter the data first and then use the HAVING clause for the aggregate data filter. If you use WHERE clause first, the number of rows scanned is limited before applying the HAVING condition.
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