Demystifying SQL Server Execution Time: Going Beyond Seconds in SSMS

• SSMS displays query execution time in the "Results" pane after running a query.
• By default, it shows the total elapsed time, which includes network communication, data retrieval, and results rendering on your client machine.
• To see the actual execution time on the SQL Server itself (excluding network overhead), you need to enable "Client Statistics."

Enabling Client Statistics:

There are three ways to enable Client Statistics in SSMS:

1. Menu:

   • Go to the "Query" menu.
   • Select "Include Client Statistics."

2. Toolbar:

3. Keyboard Shortcut:

   • Press Shift + Alt + S.

Additional Options (Optional):

• Query Options:
  • Right-click anywhere in the query editor.
  • Select "Query Options."
  • Go to the "Advanced" tab under the "Execution" group.
  • Check the boxes for "SET STATISTICS TIME" and "SET STATISTICS IO" (if desired) for more detailed performance metrics.

Viewing Execution Time in Milliseconds:

Once Client Statistics is enabled, the "Results" pane will display the following information:

• CPU time (ms): The time spent executing the query on the SQL Server's CPU.
• Elapsed time (ms): The total time taken, including network overhead and client-side processing (same as the default view).

Key Points:

• Client Statistics provides a more accurate representation of the query's execution time on the SQL Server.
• The "Elapsed time" still includes network overhead and client processing.
• "SET STATISTICS TIME" and "SET STATISTICS IO" offer further performance insights (consider using them for in-depth analysis).

Let's say you have a simple query to select all customers from a table named Customers in your SQL Server database.

SELECT * FROM Customers;

Viewing Execution Time:

2. With Client Statistics Enabled:

   • Enable Client Statistics using one of the methods mentioned earlier (menu, toolbar, keyboard shortcut).
   • Execute the same query again.

   The "Results" pane will now show additional information, including:

   (1 row affected)
   
   Client Statistics - 1 rows returned
       CPU time (ms):        2
       Elapsed time (ms):     15  -- This includes network and client processing
       Logical reads (ms):    0
       ... (other statistics)
   

   Here, you can see the "CPU time (ms): 2", which indicates the actual execution time on the SQL Server was 2 milliseconds.

Remember:

• This is just an example, and your actual execution times will vary depending on your database size, server configuration, and network conditions.

• DMVs are built-in tables in SQL Server that provide real-time performance monitoring data.
• You can use the sys.dm_exec_query_stats DMV to retrieve detailed information about query execution, including CPU time in milliseconds.

Example:

SELECT TOP 1 qs.query_id, qs.execution_count, qs.cpu_time_ms
FROM sys.dm_exec_query_stats qs
CROSS APPLY sys.dm_exec_sql_text(qs.sql_handle) AS st
WHERE st.text LIKE '%<your_query_text_here>%';

• Replace <your_query_text_here> with the actual text of your query.
• This query will retrieve the top 1 matching query (change TOP 1 if needed) and show its execution count and CPU time in milliseconds.

Using Extended Events (SQL Server 2008 R2 and later):

• Extended Events (XEvents) offer a more flexible way to capture query execution data, including CPU time.
• You can create a session to capture specific events related to query execution and configure it to record CPU time in milliseconds.

Third-party Performance Monitoring Tools:

• Several third-party tools specialize in monitoring SQL Server performance.
• These tools often provide detailed execution plans, including CPU time in milliseconds, along with other performance metrics.

Choosing the Right Method:

• Client Statistics: Easiest and quickest method for basic monitoring.
• DMVs: Good for programmatic access to detailed execution data.
• XEvents: Offers more flexibility but requires more setup.
• Third-party Tools: Provides advanced features and visualizations but might incur additional costs.

Consider the following factors when choosing a method:

• Complexity: Client Statistics is the simplest.
• Detail level: DMVs and XEvents offer more detailed execution information.
• Frequency of monitoring: If you need continuous monitoring, consider third-party tools.