Server Query Execution - Where Filtration Order - Performance Impact
Jul 27, 2015
For example in a Select Statement we have many tables and we have Where Clause with many conditions with AND operations. Do the SQL SERVER would apply the Where clause after all fetch or can dynamically decide about to include the related Tables from Select Statement Orderly with respect to where clause predicates? (SQL SERVER would not fetch data of those tables for its Select, where the AND condition in Where clause fails or by logic would be fruitless/not-related.)
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Jun 15, 2007
If I have 6-8 queries running in parallel, Whether having a Single connection Manager (for the same source) for all the Extract performs faster or having Distinct Connection Manager for each of the extract performs faster ?
Regards
Subhash Subramanyam
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May 17, 2015
What would happen to the the queries which are under execution when I change the MAXDOP value from say 0 to 1?
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Jan 18, 2001
I want to determine the performance impact caused by the extensive use of the 'select into #' statement in a production environment. The current situation is that our reports team extensively uses the 'select into #' statement to build smaller subsets of data. These subsets are then used as the basis to create summary style reports and exports. All this is accomplished via the use of SQL pass-through.
After these reports/exports are completed and tested, they are then released to our operations department and the users. The reports/exports then can be run against the production server at the discretion of the user, provided they have the appropriate permissions. These reports/exports target the live data on the primary production server that already has been designated for the use of the application software.
Now I know that reporting against a transactional-based server, where the users run the application, is not a very good idea. (Inherited) I am currently migrating all reports/exports to a reporting server. Although it will still be transaction-based, the reports/exports will be isolated from user activity. Eventually we will be moving toward a warehouse scenario.
I also know that the extensive use of the 'select into #' statement is not a coding practice for use in production. I provided several alternatives to this practice
1) insert..select 2) insert..execute - from stored procedure
I have read that in the in sql 6.5 that this may cause severe performance and locking behaviors in system db's and tempdb. However, in the following document on the Microsoft Knowledge Base, it indicates that SQL 7.0 may have corrected this issue.
Q153441 - FIX SELECT INTO Locking Behavior.htm
Despite the indication of being corrected, I am still not convinced. I am frequently seeing drastic performance hits, especially when several of the reports are running. (which is very common) My concern is that moving these reports/exports to a reporting server may save the users; I believe that it may be migrating the problem to another location. I will be working with the developers to optimize their code and will investigate index issues.
** To make a long story short. I would like someone who has experience with this provide me with the top 5+ reasons not to use the 'select into #' methodology in a production environment. Further, if anyone has any documentation, I would surely like the info.
Thanks, Dave
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Feb 19, 2004
Hi,
Anybody have any idea howmuch % of performance will be affect if we are using varchar instead of char data type?.
Thanks,
Ravi
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Apr 18, 2008
I have been collecting information about 20 performance counters (memory, IO, cpu, SQL) that refresh every 15 seconds, would that have any performance hit in the server? what are best practices when collecting information via performance counters?
Thanks
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Jan 15, 2008
I want to use "on delete cascade" in one of my tables but I'm worried though whether this can affect the performance when having millions of records. To explain more I'm working on a social networking website and I have two tables UserAccounts, in which I only keep the username and password and a few related fields, and Profiles in which I keep the profile data for users, I want to be sure that I won't have any records in the Profiles table without corresponding records in the UserAccounts table. Please see the DDL below to understand more the structure of the tables:
CREATE TABLE UserAccounts
(
UserID INT NOT NULL IDENTITY(1,1) PRIMARY KEY,
UserName VARCHAR(20) NOT NULL,
Password VARCHAR(20) NOT NULL,
--other fields (e.g. last login .. etc)
)
CREATE TABLE Profiles
(
UserID INT NOT NULL REFERENCES UserAccount(UserID),
-- other fields (e.g. birthdate, nationality .. etc)
)
Any suggestions are highly appreciated...
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Jul 20, 2005
Hi all,Just wondering if anyone can tell me if an order by clause on a selectquery would have any impact on the time it takes to retrieve results?Essentially I'm selecting Top 1 out of a table via various criteriaand currently getting it back without an order by clause. The order bywould only include the column that has the clustered primary index onit.Can anyone tell me if in theory this will slow the query down?Many thanks in advance!Much warmth,Murrau
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Jun 21, 2007
Hello All,
When creating my database I have modeled some of the tables after the Adventureworks sample database.
There are some fields or entire tables in Adventureworks that I do not see an imediate use for, however; I would hate to ommit them to find out later they would have been benificial. (.eg territory table).
In general terms what would the impact be on size and performance of a database which contains tables or fields that do not contain data.
Thanks for your help!
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Jan 16, 2014
Curious if I have the code below as an example and I execute this code does sql execute from top to bottom? And does the Update run and complete before the delete occurs? Or does SQL execute the update and delete in parallel?
UPDATE tbl1 SET col1 = 1
GO
DELETE FROM tbl1 where col2 = 2
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Jun 5, 2001
I want a task to run last after all of the other task have run. How do I ensure that this task will run last?
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Aug 28, 2006
If I have a List with three tables in it, and let's say that in the first two
tables, I'm adding something to a global variable and in the 3rd table I'm
calling that global variable...can I be 100% sure that the call to that global
variable in the 3rd table will always be the result from the first two
tables?
I mean will it always be true that the first two tables are analyzed and
"executed" before that third table?
Thanks for any help. If there are any links on this topic on the microsoft
web site, please specify them. I have not been able to find anything
Thank you!
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Nov 17, 2004
I have a package that has 12 data pump tasks all executing in parallel.
It is transferring raw data from an AS400 DW to a MSSQLSvr Staging area.
Each pump task on completion assigns values to a set of global variables, then having done this passes these as parameters to a sproc which inserts them into a table.
This seems to work for 4 or 5 of the pump tasks but, the rest of the rows in the table are all the same because the remaining pump tasks are all executing before the sprocs.
Is there a way to make sure that the entire set of job steps completes, before starting another job set of steps while still keeping them running in parallel.
I had wondered if there was a way to use the PumpComplete phase of each pump step to fire off the sproc, but can't see how you execute the step.
Any ideas would be much appreciated.
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May 20, 2006
Hi,
Is there any way to enforce task execution order within a control flow? I need to have tasks execute after each other, because for example Task B depends on the execution of Task A.
Doesn't the success constraint enforce execution order? When I run my package the tasks seem to execute in a random order which is not what I want.
What I am trying to do is:
Loop through all Xml files in directory
For each Xml file:
For categories, products & fields:
Truncate staging table
Insert data from Xml file into staging table
After all Xml files have been processed then import data from staging to main tables
Here is my control flow:
http://www.myfootballonline.com/flow.png
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Nov 14, 2007
I have nested lists and I want to set a global value in my custom code AFTER a specific table footer row. Does anybody know in what order the table elements are rendered? I have tried adding my piece of code into a group value, the hidden property, the color property, and sending it as a parameter to a subreport, but it still sets that variable first before rendering the table footer row that I want to display before I set that variable. I have been pulling my hair out trying to do this one! Help!
BJ
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Feb 29, 2008
Is the order of execution guaranteed to go from top to bottom in a transaction that has multiple statements like below?
BEGIN TRAN T1;
UPDATE table1 ...;
UPDATE table2 ...;
SELECT * from table1;
UPDATE table3 ...;
COMMIT TRAN T1;
How about here?
BEGIN TRAN T1;
UPDATE table1 ...;
BEGIN TRAN M2 ;
UPDATE table2 ...;
SELECT * from table1;
COMMIT TRAN M2;
UPDATE table3 ...;
COMMIT TRAN T1;
how can i guarantee that statements will be executed from top to bottom in a transaction batch like above? I am not interested in the errors in statements. I just want whole thing to either execute fully from top to bottom or none executes
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Sep 4, 2006
How can I get and or set the order in which the cascading deletes of a table are executed??
I have table A with cascading deletes to Table B and Table C. Records in table B can not be deleted if they are referenced from table C. So if I delete C, then B and then A; that would work. But B then C and then A might be prohibited due to the constraint between B and C. Therefor the order of execution of the cascading delete is important.
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Mar 18, 2008
Hello All,
I have a Conditional Split, where there are two outputs.
First output is a dataset which is to be inserted into the database.
Second output is a dataset for which the data already exists in the DB. I just need to update those data.
I have a doubt here. I want the insertion to be done first and then updation.
Is there any property to be set for insertion or updation, something that maintains the order of execution or priority of execution.
Please do ask me if you need any further clarification.
Thanks,
Kapadia Shalin P.
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May 27, 2008
Hi
I am designing a ETL system to extract data from multiple systems. I have designed a batch control application and database to manage the process. I was thinking of extending this to include the execution of the SSIS packages. I would basically store all of the package details in the database, and when I am executing a particular systems load, I would get the list of packages required and loop through them in a ForEach loop. The question I have is can I guarantee the order of execution? I will put an order or execution in the DB and when I select the data, I can order by these columns.
I am concerned that in putting the data into a record set in SSIS its order could be changed resulting in the packages executing incorrectly.
Has anyone done anything similar to this and and run into problems, or is it not an issue?
Many Thanks
Michael
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Sep 21, 2015
I am executing a CUBE which is having 9 measure groups, i need to know order of the execution of the measure groups.??
ex:
1. fsales
2.ftranssales
3.fitem
4.fstores..............etc...
I know, the dimension are executed first, but not aware of the order of execution of measure group.
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Jun 9, 2006
Hi,
I'm facing a problem with my SSIS package regarding the execution order of tasks. I am using my package for the purpose of loading data from XML to staging tables in the database, and have a loop to process all XML files.
As a precondition to the loading action itself, I am running a stored procedure against the database (using the ExecuteSQL task) to check whether all staging tables are empty. The output parameter of that stored procedure is mapped to a variable I have defined in the SSIS package, so I can use it as a basis for the decision whether to run the loading action or not.
In order to test my package I added a script task, right after the execution of the stored procedure with a precedence constraint, that pops up a messagebox with the value of the stored procedure return value stored in the package variable.
The problem is that for the first iteration of the loop, the variable value presented by the messagebox is incorrect (equals to the initial value I assigned to the variable), and it looks like the script task starts before the stored procedure execution task finishes and its output value is stored in the package variable.
Please assist.
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May 16, 2008
I've been working with SQL Server 2005 for a while now and I've noticed some odd behavior that I want to bounce of other members of the community. I should preface that I've been a forum viewer (and occasional contributer) here at SQL Team for a while and I've naturally developed a keen sense for optimizations.
Fundamentally, longer stored procedures with perfectly fine/optimized execution plans are inconsistent with real world performance. In some of these cases, a low subtree cost on a 4 core machine with 16gb of ram and 2 15 drive SAS arrays with little load takes excessively long to run or in some cases doesn't complete.
This isn't due to blocking or resource bottlenecks as I'm quite familiar with built in tools to troubleshoot and resolve those issues. In all cases, I am able to rearchitect the stored procedure into a higher subtree cost variant and get reasonable performance, but it's frustrating to have to redo work and there seems to be no common theme other than longer multi-statement procedures.
I've used SQL Server 2000 extensively and did not notice this level of inconsistency in performance with that product version. Just wondering if others in the community have experiences similar or if I'm just crazy.
Thanks for reading my rant.
- Shane
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Apr 16, 2007
Hi,
We have a process that builds our data warehouse.
The processes execute SPs in serial order.
Each SP builds separate table.
Each table is build destructive (truncate and Insert Into).
I've tried to change the configuration by running 4 SP in parallel by SSIS to shorten the update time.
I've noticed in two declines in performance:
1. Each SP execution time is higher in the parallel execution in around 50% then in the serial execution. The CPU utilization is the same.
2. On each parallel execution we have a decline in performance of around 5 -10% compare to the previous parallel execution.
Do you have any directions to inquire?
Btw €“ we have Itanium 64bit x8 with 32GB memory
Thanks,
Assaf
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Jan 23, 2008
Has anyone encountered cases in which a proc executed by DTS has the following behavior:
1) underperforms the same proc when executed in DTS as opposed to SQL Server Managemet Studio
2) underperforms an ad-hoc version of the same query (UPDATE) executed in SQL Server Managemet Studio
What could explain this?
Obviously,
All three scenarios are executed against the same database and hit the exact same tables and indices.
Query plans show that one step, a Clustered Index Seek, consumes most of the resources (57%) and for that the estimated rows = 1 and actual rows is 10 of 1000's time higher. (~ 23000).
The DTS execution effectively never finishes even after many hours (10+)
The Stored procedure execution will finish in 6 minutes (executed after the update ad-hoc query)
The Update ad-hoc query will finish in 2 minutes
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Jul 20, 2005
Hi All,I have a table that currently contains approx. 8 million records.I'm running a SELECT query against this table that in somecircumstances is either very quick (ie results returned in QueryAnalyzer almost instantaneously), or very slow (ie 30 to 40 seconds toreturn results), and I'm trying to work out how I improve performance.Essentially the query I'm running is nothing more complex than:SELECT TOP 1 * FROM Table1 WHERE tier=n ORDER BY member_id[tier] is a smallint column with a non-clustered, non-unique index onit. [member_id] is a numeric column with a clustered, unique index onit.When I supply a [tier] value of 1, it returns results instantaneously.I have no idea if this is meaningful, but the tier = 1 records wereloaded first into the table, and comprise approximately 5 millionrecords.When I supply a [tier] value of 2, the results take 30 to 40 seconds.tier =2 records were loaded second, and comprise approximately 3million records.I've tried running an execution plan, and while I'm no expert, itappears to me that the index on tier isn't being used, even if I use:tier = CAST(2 as SMALLINT)I'm wondering if anyone can give me ANY advice on how to get anybetter performance out of this SELECT statement?Also, out of curiosity, can a disk defragment have a positive impacton SELECT query performance?Any help very much appreciated!Much warmth,Murray
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Jul 23, 2005
Does the order in which Joins are peformed (from left to right) matterwhether inner or outer when it comes to performance. Assuming that allindexes are the same but the size of the tables is different?For example let's assume we have 5 tables, TABLE1, TABLE2, TABLE3,TABLE4, TABLE5.For example:SELECT Smth from TABLE1 INNER JOIN TABLE2 on Condition1INNER JOIN TABLE3 on Condition2LEFT JOIN TABLE4 on Condition3INNER JOIN TABLE5 on Condition4.Does SQL optimize the query and finds the best way to inner join or itstarts doing the JOINS from left to right?Thank you for your your feedback.Gent
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Mar 31, 2008
I am using SQL2005 EE with SP1. The server OS is windows 2K3 sp2
I have a table-valued function (E.g. findAllCustomer(Name varchar(100), gender varchar(1)) to join some tables and find out the result set base the the input parameters.
I have created indexes for the related joinning tables.
I would like to check the performance of a table-valued function and optimize the indexing columns by the execution plan.
I found the graphic explanation only show 1 icon to represent the function performance. I cannot find any further detail of the function. (E.g. using which index in joinning)
If I change the function to stored procedure, I can know whether the T-SQL is using index seek or table scan. I also found the stored procedure version subtree cost is much grether that the table-valued function
I would like to know any configureation in management studio can give more inform for the function performance?
Thanks
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Jan 4, 2005
Thanks to all participants.
I am using SQL Server 2000 with replication object for two location. Log size on publisher go upto 25 times of data file size, I mean 80 MB Data files has maintains 2 GB log file and it is same for all five co's working on same windows 2000 advanced server board.
Since last week server randamly get disconnected from user applications and at that time few tables are not openable at server.
Can any one give a reason ? Why this type misbehaviou done by SQL Server 2000?
Thanks.
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Sep 1, 2007
We have the following scenario:
Server A replicates Database A to Server B.
Server C has Database A on it as well, but in standby mode. We are applying the transaction logs generated by Database A on Server A to the database on Server C leaving it in standby mode each time.
Let's say we had planned maintenance for Server Aand dumped the last set of transactions on Server A in standby mode to be applied to to Server C. What happens to the replica on Server B? When I start to use Server C, can I backup its transactions and apply them to Server A, and then have those transactions replicated to Server B? And then what do I do when the maintenance is complete so that I can swithc back to Server A and have the replication continue on as before the maintenance to Server B?
Thanls
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Aug 5, 2015
Our SQL Server 2008 r2 has collation Latin general.
And my database 'DB1' , 'DB2' has collation set to Japanese unicode.
My sql team has informed they cannot change system collation as it hosts other db's as well.
My Query: What will be the impact of changing collation from JP to Latin.
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Aug 22, 2014
Set up a trace with the events RPC:Completed, SQL:BatchCompleted, SQL:BatchStarting, and SQL:StmtCompleted.
When I issue the statement: SELECT * FROM XyzView there is nothing captured in Profiler. If I script out the view and then execute the select statement that defines the view, it does show up in Profiler.
I've tried adding a lot of the other events, i.e. SP:StmtCompleted and the various other StmtStarting events and the trace still does not capture anything.
Am I capturing the wrong events or is this known behavior? My goal is to see what the overhead is for using a view versus persisting the results of the view as a table and referencing that instead. The view in question is against static data, joins 9 tables, and is referenced a lot.
I can use the stats generated when I execute the select that defines the view but I still find this to be curious behavior so I assume I'm doing something wrong.
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Jun 17, 2015
Is it possible to check query execution plan of a store procedure from create script (before creating it)?
Basically the developers want to know how a newly developed procedure will perform in production environment. Now, I don't want to create it in production for just checking the execution plan. However they've provided SQL script for the procedure. Now wondering is there any way to look at the execution plan for this procedure from the script provided?
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Sep 9, 2015
I would like to view the previous executed query error message in SSMS. Is there any way to view the query execution error messages history in SSMS?
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