SQL optimisation : How to find out the most used T-SQL queries ?

Provided you have the required autorisations to run those SCRIPTS, here are handfull T-SQL query to find out the most used queries within the SQL Server's cache (since the last reboot).

Thank you Christian Robert !
SELECT

      LEFT(tx.text, 50) AS 'Query',

      SUM(qs.total_logical_reads) 'Logical Reads'

FROM

      sys.dm_exec_cached_plans AS cp

      JOIN sys.dm_exec_query_stats AS qs

      ON cp.plan_handle =qs.plan_handle

      CROSS APPLY sys.dm_exec_sql_text(cp.plan_handle) AS tx

--WHERE qs.max_logical_reads> 0 And (0. + qs.min_logical_reads) / (0. + qs.max_logical_reads ) > 0.1

GROUP BY LEFT(tx.text, 50)

ORDER BY 2 DESC

Another version by pinaldave :

SELECT TOP 10

    qt.TEXT AS 'SP Name',

    qs.execution_count AS 'Execution Count',

    qs.total_worker_time/qs.execution_count AS 'AvgWorkerTime',

    qs.total_worker_time AS 'TotalWorkerTime',

    qs.total_physical_reads AS 'PhysicalReads',

    qs.creation_time 'CreationTime',

    qs.execution_count/DATEDIFF(Second, qs.creation_time, GETDATE()) AS 'Calls/Second'

FROM

    sys.dm_exec_query_stats AS qs

    CROSS APPLY sys.dm_exec_sql_text(qs.sql_handle) AS qt

WHERE

    qt.dbid = (

        SELECT dbid

        FROM sys.sysdatabases

        WHERE name = 'AdventureWorks')

ORDER BY

    qs.total_physical_reads DESC

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SET STATISTICS IO ON;