Find Most Expensive Queries Running on a Table I was investigating SQL Server performance issue on a table where I was getting more locks, query timeout expires, on a table that has more than a hundred columns. So I was just wanted to know what are the most expensive queries running on that SQL Server table. I would like to share my script that will return most expansive query running on a table, Hare I am using DVM to find the most expansive query. Suppose we have a table called calls SELECT TOP 15 SQLQueries=SUBSTRING(qt.TEXT, (qs.statement_start_offset/2)+1, ((CASE qs.statement_end_offset WHEN -1 THEN DATALENGTH(qt.TEXT) ELSE qs.statement_end_offset END - qs.statement_start_offset)/2)+1), qs.execution_count, qs.total_logical_reads, qs.last_logical_reads, qs.total_logical_writes, qs.last_logical_writes, qs.total_worker_time, qs.last_worker_time, qs.total_elapsed_time/1000000 total_elapsed_time_in_S, qs.last_elapsed_time/1000000 last_elapsed_time_in_S, qs.last_execution_time, qp.query_plan FROM sys.dm_exec_query_stats qs CROSS APPLY sys.dm_exec_sql_text(qs.sql_handle) qt CROSS APPLY sys.dm_exec_query_plan(qs.plan_handle) qp where SUBSTRING(qt.TEXT, (qs.statement_start_offset/2)+1, ((CASE qs.statement_end_offset WHEN -1 THEN DATALENGTH(qt.TEXT) ELSE qs.statement_end_offset END - qs.statement_start_offset)/2)+1) like '% calls %' -- ORDER BY qs.total_logical_reads DESC -- logical reads -- ORDER BY qs.total_logical_writes DESC -- logical writes ORDER BY qs.total_worker_time DESC -- CPU time The above script will return the most expansive query running on “calls” table. you can change the order by clause on Logical reads, Logical writes or on CPU time. Please note : Running in your environment replace “calls” from script to your table name. ie % calls %

What are the back-end processes when we type "Select * from Table" in Oracle?

Parvez

What are the back-end processes when we type "Select * from Table" in Oracle?

Seema

First, it will look into the System Global Area (SGA) weather query is been executed earlier.
If it exists, it would retrieve the same output present in memory.

If not the query we typed complies and the resulting parse tree and execution plan is been stored in SGA. Then the query gets executed and the output is given to the application.