Performance On Update Query
Jan 23, 2008
Hi,
My friend expresses his concern over the performance of his update query.
He says the execution time takes around 120 ms.
the query is looking like
Update table set col1 = 'value', col2 = 'val', col3= 'val'............ col40='val'
where col1 = 'value' and col2 = 'value' and col3 = 'val' and col4 = 'val'
He says he's updating around 40 columns at a stretch with filter conditions as shown, and only 1 row is getting affected by this.Where the col1, col2,col3 n col4 are composite primary keys and have default clustered indexes created on them.
Is that the execution time he say is really a performance issue ? I'm confused on this
Experts, pls post your comments and any tips on improving update query in general will immensely help.
thanks,
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Jun 23, 2006
Hello Everyone,I have a very complex performance issue with our production database.Here's the scenario. We have a production webserver server and adevelopment web server. Both are running SQL Server 2000.I encounted various performance issues with the production server with aparticular query. It would take approximately 22 seconds to return 100rows, thats about 0.22 seconds per row. Note: I ran the query in singleuser mode. So I tested the query on the Development server by taking abackup (.dmp) of the database and moving it onto the dev server. I ranthe same query and found that it ran in less than a second.I took a look at the query execution plan and I found that they we'rethe exact same in both cases.Then I took a look at the various index's, and again I found nodifferences in the table indices.If both databases are identical, I'm assumeing that the issue is relatedto some external hardware issue like: disk space, memory etc. Or couldit be OS software related issues, like service packs, SQL Serverconfiguations etc.Here's what I've done to rule out some obvious hardware issues on theprod server:1. Moved all extraneous files to a secondary harddrive to free up spaceon the primary harddrive. There is 55gb's of free space on the disk.2. Applied SQL Server SP4 service packs3. Defragmented the primary harddrive4. Applied all Windows Server 2003 updatesHere is the prod servers system specs:2x Intel Xeon 2.67GHZTotal Physical Memory 2GB, Available Physical Memory 815MBWindows Server 2003 SE /w SP1Here is the dev serers system specs:2x Intel Xeon 2.80GHz2GB DDR2-SDRAMWindows Server 2003 SE /w SP1I'm not sure what else to do, the query performance is an order ofmagnitude difference and I can't explain it. To me its is a hardware oroperating system related issue.Any Ideas would help me greatly!Thanks,Brian T*** Sent via Developersdex http://www.developersdex.com ***
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Oct 20, 2002
I should add an Identity field (Identity=True) and a row version field(timestamp) to my table, and avoid to arrange tables into different databases, is it true in general?
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Nov 6, 2007
Recently we moved few of our databases from SQL 2000 to SQL 2005 (SP 2) using backup and restore. After the restore I did Reindex and update stats on the databases. Since then we have observed performance issues on SQL 2005 databases but this performance problem vanishes the moment we run (sp_updatestats). Is this a problem with SQL 2005 that we have to run sp_updatestats 2 times a days or 3 times a day. In SQL 2000 we ran it only Once a week and still we never had any performance issues. Is there any config change we need to do to fix this problem in SQL 2005?
Thanks !
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May 8, 2006
Hi,I have an UPDATE statement which runs very slow (about 1-2 minutes) inWeb as well as in Query Analyzer. Very plain UPDATE statement; usesindexes, etc. I though the reason might be the table being unorganizedbecause of the row expansions due to updating an existing column valuewith a larger value. Therefore, I ran a maintanenance plan whichreorganizes data and rebuilds indexes. But, it seems that there is noimprovement.Any thought or advise will be greatly appreciated.Sincerely,Pelin Bali.
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Jun 26, 2007
Hello!I have this piece of SQL code:UPDATE aSET Field1 = c.Field1FROM aINNER JOIN b ON a.GUID1 = b.GUID1INNER JOIN c ON b.GUID2 = c.GUID2WHERE c.Type = 1AND @date BETWEEN b.DateFrom AND b.DateToThis query takes hours to complete.Now while trying to find out what's causing the poor performance (itsurely looks simple enough!) I've rewritten it to use temp tables:SELECT a.GUID1, a.Field1, c.Type, b.DateFrom, b.DateTo INTO #temptableFROM aINNER JOIN b ON a.GUID1 = b.GUID1INNER JOIN c ON b.GUID2 = c.GUID2WHERE c.Type = 1AND @date BETWEEN b.DateFrom AND b.DateToUPDATE a SET Field1 = subsel.Field1FROM (SELECT * FROM #temptable) AS subselWHERE subsel.GUID1 = a.GUID1Now it completes in 10 seconds.My question is why? Am I wrong in saying that the two batches aboveproduce same results? Is there something I've missed about the UPDATEFROM syntax? Why would the first query perform THAT poorly?Table sizes:a: 24k rowsb: 268k rowsc: 260k rowsGUIDs are of type uniqueidentifier.Any answers appreciated!Regards,// Richard
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Jul 20, 2005
Dear Sql Server experts:First off, I am no sql server expert :)A few months ago I put a database into a production environment.Recently, It was brought to my attention that a particular query thatexecuted quite quickly in our dev environment was painfully slow inproduction. I analyzed the the plan on the production server (itlooked good), and then tried quite a few tips that I'd gleaned fromreading newsgroups. Nothing worked. Then on a whim I performed anUPDATE STATISTICS on a few of the tables that were being queried. Thequery immediately went from executing in 61 seconds to under 1 second.I checked to make sure that statistics were being "auto updated" andthey were.Why did I need to run UPDATE STATISTICS? Will I need to again?A little more background info:The database started empty, and has grown quite rapidly in the lastfew months. One particular table grows at a rate of about 300,000records per month. I get fast query times due to a few well placedindexes.A quick question:If I add an index, do statistics get automatically updated for thisnew index immediately?Thanks in advance for any help,Felix
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Jul 20, 2005
hiFor an unavoidable reason, I have to use row-by-row processing(update) on a temporary table to update a history table every day.I have around 60,000 records in temporary table and about 2 million inthe history table.Could any one please suggest different methods to imporve the runtimeof the query?Would highly appreciate!
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Jul 20, 2005
Below is a simple UPDATE that I have to perform on a table that hasabout 2.5 million rows (about 4 million in production) This queryruns for an enourmous amount of time (over 1 hour). Both theChangerRoleID and the ChangerID are indexed (not unique). Is thereany way to performance tune this?Controlling the physical drive of the log file isn't possible at ourclient sites (we don't have control) and the recovery model needs tobe set to "Full".UPDATE CLIENTSHISTORY SET ChangerRoleID = ChangerID WHEREChangerRoleID IS NULLAny Help would be greatly appreciated!
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Apr 23, 2008
Hi All,
Not sure if this question belongs in this area or the server area but I'll start here. Here is my problem. We have an C/C++ app that was originally written for SQL 2000 and uses DBLibrary. We have converted it to SQL 2005 and are using ODBC/Native client to access the SQL 2005 database. This all works great. So we were doing some performance testing and we noticed that our update performance seems slower in the SQL 2005/ODBC case than it did in the SQL 2000/DBLibrary case. Inserts and queries all perform great, in fact the inserts are significantly faster in the SQL 2005/ODBC case which is good. We are using Array inserts/updates/queries wherever possible as this is faster obviously. In our update case, it takes 1.14 seconds to update 2000 rows in table in the SQL 2005/ODBC case, while SQL 2000/DBLibrary case takes .39 seconds to the exact same thing. The table in question is a 12 column table with all integer columns, with an index on the first three columns.
So my question is this. Is there something different about Array Updates in SQL 2005 ? I've looked thru the list of hot fixes available since SQL 2005 SP2 and haven't seen anything that directly mentions Updates so I'm hesitant to go off and start applying the hot fixes to our server to see if the behavior changes. It seems strange to me that Array Inserts would be very fast, but Updates wouldn't be. I've checked the ODBC Data Source and we aren't doing anything fancy there. I'm not actually even sure if this problem is client side or server side as I said earlier.
If anyone has any ideas or thoughts that would be great since this is really bugging me.
Here is a sample of what our C code is doing. This is simplied and I've removed a lot of our own code but these are the SQL calls that we are making in order so maybe can see something wrong I'm doing.
//----Sample Code -------------------------------------------------------------------------------------
pSQL = "Update bob set VV=? where VI=?" // not done this way actually in our code but just to show the update text
status = SQLPrepare ( hS, (UCHAR *)pSQL, SQL_NTS );
// Called twice with nCol = 1 and then with nCol = 2
status = SQLSetParam (
hS,
abs(nCol),
cType, // cType = 5 = SQL_C_LONG
sqlType, // sqlType = 4 = SQL_INTEGER
38, // size needed in case the column is numeric or decimal
0,
p16Data, // Pointer to my array of data
NULL
);
SQLSetStmtAttr(hS, SQL_ATTR_PARAMSET_SIZE, (SQLPOINTER)numrows, 0); // numrows = 2000
SQLSetStmtAttr(hS, SQL_ATTR_PARAMS_PROCESSED_PTR, &p16cRows, 0);
status = SQLExecute (hS);
SQLParamOptions(hS, 1, NULL);
SQLFreeStmt ( hS, SQL_RESET_PARAMS );
//----Sample Code -------------------------------------------------------------------------------------
Thanks,
Nick
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Oct 2, 2007
If I run sp_updatestats, does it effect performance?
My testing also reveals canceling sp_updatestats, doesn't caus a rollback?
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Oct 16, 2013
I need to figure out the correct update statement syntax for the following integration.
I have a "Performance Table" which i insert weekly performance numbers into for each store. The table is constructed w/ columns such as Store, Weekenddate, Sales, Refunds, #ofPatients
In a "Averages Table" i have every weekenddate for each store populated. So 52 Weeks for 10 stores = 520 Rows of Store numbers & WeekendDates.
What i would like to do is run a loop or update statement which would update the store average for each weekendate based on the last 13 weeks.
This is my query
update performancestore_avgs set SalesAvg =
(select sum(SalesHit)/Count(Store) from performance_store where performance_store.weekenddate >= performancestore_avgs.weekenddate-84 and performancestore_Avgs.store = performance_store.store)
The update statement runs but the averages are completely wrong.
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Oct 25, 2007
I installed the SQL Server 2005 SP2 update 2 rollup on my 64-bitserver and the performance has tanked!I installed rollup 3 on some of them, but that did not seem to help.I thought it was just a linked server performance issue, but myoptimization started running today on one of the "update 2" instancesand so far it's been running about 10 hours longer than it normallydoes.The rollup 3 fixed our stack dumping issues, but we NEED to have thisperformance thing fixed!I saw that MS has come out with update 4 last week - doesn't sayanything about fixing this, though.Has anyone else experienced this?I'm not necessarily expecting anyone to have a fix for this, justwantto know I'm looking in the right place before I call MS.
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Feb 21, 2007
We recently implemented merge replication.We were expereincing. The replication is between 2 SQL Servers (2005) over same network box, and since we have introduced the replication, the performance has degraded considerably on subscriber end.
1) One thing that should be mention is that its a "unidirectional Direction" flow of changes is from publisher towards subscriber (only one publisher and distributor as well and one subscriber ).
2) Updates are high than inserts and only one article let say "Article1" ave update up to 2000 per day and i am experiecing that dbo.MSmerge_upd_sp_Article1_GUID taking more cpu time.what should be do..
on subscriber database response time is going to slow and i am experiencing a lot of number of LOCK time outs on application end.
can any one can also suggest me server level settings for aviding locking time out.
looking for any experieced solution/suggestion.
Thanks in advance.
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Mar 26, 2007
Hi! Select gets all records that contains illegal chars... Ok, to replace '[' { and some other chars I will make AND '% .. %' and place other intervals, that is not the problem.The problem is: How to replace not allowed chars ( ! @ # $ % ^ & * ( ) etc. ) with '_' ?I have seen that there is a function REPLACE, but can't figure out how to use it. 1 SELECT user_username
2 FROM users
3 WHERE user_username LIKE '%[!-)]%';
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May 19, 2004
Hi..
Is there any specific place where I can find which SQL Query is more efficient?.
Is INNER JOIN is faster or Select ... Where ID in (SELECT ...) is faster?
I have two tables:
1.FLEET (The number of rows is not so much)
Attributes :
Company_Id (PK)
Fleet_Id (PK)
Fleet_Name
Fleet_Description
2.USER_PRIVILEGE (The number of rows can reach up to 3 times the number of row in fleet table)
Attributes :
Company_Id (PK)
Fleet_Id (PK)
User_Id (PK)
Privilege_Id(PK)
Comment
Category
I want to select Fleet_Id and Fleet_Name from fleet table
Where the current user has privilege_id=1
I have two possible select statement :
1.Option 1
SELECT Fleet_Name, Fleet_Id
FROM FLEET
WHERE (Company_Id = 2) AND (Fleet_Id IN
(SELECT fleet_id
FROM user_privilege
WHERE user_id = 11 AND company_id = 2 AND privilege_id = 1))
ORDER BY Fleet_Name
2.Option 2
SELECT F.Fleet_Name, F.Fleet_Id
FROM USER_PRIVILEGE U INNER JOIN
FLEET F ON U.Fleet_Id = F.Fleet_Id
WHERE (F.Company_Id = 2) AND (U.Privilege_Id = 1) AND (U.User_Id = 11)
ORDER BY F.Fleet_Name
Actually which one is faster. Is SQL Statement with INNER JOIN (Option 2) can be executed faster than the one with double Select Statement(Option 1)?
Any suggestion is welcomed.
Thank you very much.
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Dec 12, 2005
Hi:
I have the following query, can somebody help me?
SELECT s.Id, s.NameFROM Switch s INNER JOIN SwitchTelephoneRange r ON s.Id = r.IdWHERE '1526858' BETWEEN FromTelephone AND ToTelephone
Where the '1526858' is a phone number.
My problem is, I want to run the above query for each record in :
select Telephone from PhoneDirectory
So, each telephone number in the second phone, would macth the ' ' in the first query.
How can I do so? Do I need a loop? a cursor? Can you help please?
Thanks
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Nov 14, 2003
Hi,
I want to know query execution time as output. I want execution time only. this is for tuning purpose... Time displayed in the status bar is not helpful for me.
thanks.
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Mar 25, 1999
Hi there,
I'm having a big performance problems with sql query. What i have done is changes physical layout (rearanged the columns) in one of the tables in the database. I used bcp to get the data out and then in. There are about quarter million rows in the this table. I have created the same indexes but know the same query takes a long time to execute. I have noticed that the showplan is somehow different than it used to be. This query uses the table i have changed and another one that i haven't touched. I have updated the stats to no help.
Here are the show plans.
this one is slow
STEP 1
The type of query is INSERT
The update mode is direct
Worktable created for ORDER BY
FROM TABLE
SW_PERSON
Nested iteration
Index : swiPERSON10
FROM TABLE
SW_CASE
Nested iteration
Table Scan
TO TABLE
Worktable 1
STEP 2
The type of query is SELECT
This step involves sorting
FROM TABLE
Worktable 1
Using GETSORTED Table Scan
this one used to be fast
STEP 1
The type of query is INSERT
The update mode is direct
Worktable created for ORDER BY
FROM TABLE
SW_CASE
Nested iteration
Table Scan
FROM TABLE
SW_PERSON
Nested iteration
Index : PK_SW_PERSON_1__27
TO TABLE
Worktable 1
STEP 2
The type of query is SELECT
This step involves sorting
FROM TABLE
Worktable 1
Using GETSORTED Table Scan
I think the problem is with the fact that the fist one doesn't use the PK
key which is the one the links both tables. My question is how to force the query to use this index.
PS.
One thing i haven't done is to recreate indexes on the other table. But i don't think that would have made a differnece.
Thanks
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Oct 16, 2006
I have the following functions in my database
Code:
CREATE FUNCTION dbo.fnProductsRetrieveBySupplierID
(
@SupplierID int
)
RETURNS TABLE
AS
RETURN
(
SELECT *
FROM Products
WHERE SupplierID = @SupplierID
)
CREATE FUNCTION dbo.fnSuppliersRetrieveBySupplierID
(
@SupplierID int
)
RETURNS TABLE
AS
RETURN
(
SELECT *
FROM Suppliers
WHERE SupplierID = @SupplierID
)
I have been testing the performance of the following SQL statements:
Code:
1.
SELECT *
FROM Products INNER JOIN
Suppliers ON (Products.SupplierID = Suppliers.SupplierID)
WHERE Products.SupplierID = 3
2.
SELECT *
FROM dbo.fnProductsRetrieveBySupplierID (3),
dbo.fnSuppliersRetrieveBySupplierID (3)
I have built a loop to execute each statement multiple times and then compare the execution times. Although both queries produce the same result, the 2nd one (which uses the functions) is about twice as slow, does anyone know why?
thanks
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May 21, 2006
Hi All,
I am joining three tables each table has got about 1.5 million rows,selecting data from these three tables and inserting into a table,to avoid transaction log issues I am running the query in a batch of size 50,000 rows,it is taking about 5hrs to insert all the 1.5 millions rows.
All the columns in the where clause have proper indexes,I ran show plan for the query and it is using indexes properly and not doing any table scan.I updated the statistics for all the indexes also.
query looks some thing like this.
insert into table d (col1,col2,col3,.............. )
values (a.col1,b.col2,c.col3 .....................)
from a,b,c
where a.id = b.id
and a.id = c.id
and a.id in between @minid and @currid
The @minid starts from 1 and @currid starts from 50000 ,I am running this in a loop, in next iteration @minid will become 50001 and currid 100,000 and so on.
Any idea why it is taking that much time?.
Thanks in advance,
bsr.
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Jan 22, 2004
I have two tables.
Employee
EmployeeCode int Primary Key
Employee_Stock
EmployeeCode int
StockCode varchar(10)
Primay key on (Employeecode, StockCode)..
There is no foreign key relation between these 2 tables.
Now my question is which query give more performance. and why?
1. Select * from
Employee INNER JOIN Employee_Stock on Employee.Employeecode = Employee_Stock.EmployeeCode
2. Create a foreign Key between Employee and Employee_Stock for EmployeeCode. and run the same query.
Actually we forgot to put the foreign key relationship between these 2 tables and we have lot of queries joining them..
Now if we add foreignkey, is it going to improve the performance or not?
Thanks
Ramesh
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Apr 8, 2008
I wrote a query and I use cursor in the query. When I run the query on dev box it takes 3 mins.
I moved the query to EPM database box and it takes forever to run.
Usually EPM database query performance is much better. How do I start debugging the poor performance?
How can I check if the query is creating any table locks?
Purpose of query: I get all the Companies (20000) and loop thru each company in the cursor and do calculations.
Thanks...
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Jun 27, 2007
Hi all
I want to check the query performance
How I should starT
I mean what is the plan to be followed
Thanks In Advance
Malathi Rao
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Mar 9, 2008
I have a query like below and it takes a aouple of seconds to run
select a.Registration_Key, ag.Agreement_Type_Name,p.ServiceProvider from dbo.Assessment a
INNER JOIN (
select distinct Registration_Key, p.ServiceProvider, max(CSDS_Object_Key) as [Sequence]
from dbo.Assessment a
INNER JOIN dbo.CD_Provider_Xref p
ON a.Provider_CD = p.Provider_CD
where Creation_DT >= '07/01/2007'
and Reason_CD = 1
group by Registration_Key, p.ServiceProvider
) as s1
ON a.CSDS_Object_Key = s1.Sequence
INNER JOIN dbo.CD_Provider_XREF p
ON a.Provider_CD = p.Provider_CD
INNER JOIN dbo.CD_Agreement_Type ag
ON ag.Agreement_Type_CD = a.Agreement_Type_CD
LEFT OUTER JOIN (
select distinct Registration_Key, p.ServiceProvider
, 1 as served
from dbo.Encounters e
INNER JOIN dbo.CD_Provider_Xref p
ON e.Provider_CD = p.Provider_CD
where Encounter_Begin_DT between '08/01/2007' and '08/31/2007'
and Procedure_CD is not null
and Encounter_Units > 0
) as s2
ON a.Registration_Key = s2.Registration_Key
and p.ServiceProvider = s2.ServiceProvider
group by a.Registration_Key, ag.Agreement_Type_Name, p.ServiceProvider
However, if i add a served field( stamped with 1) it takes forever to run.. All of join columns have indexes.. cluster and non-clustered.. and i don;t see any index fregmentaitons...
select a.Registration_Key, ag.Agreement_Type_Name,p.ServiceProvider, served from dbo.Assessment a
INNER JOIN (
select distinct Registration_Key, p.ServiceProvider, max(CSDS_Object_Key) as [Sequence]
from dbo.Assessment a
INNER JOIN dbo.CD_Provider_Xref p
ON a.Provider_CD = p.Provider_CD
where Creation_DT >= '07/01/2007'
and Reason_CD = 1
group by Registration_Key, p.ServiceProvider
) as s1
ON a.CSDS_Object_Key = s1.Sequence
INNER JOIN dbo.CD_Provider_XREF p
ON a.Provider_CD = p.Provider_CD
INNER JOIN dbo.CD_Agreement_Type ag
ON ag.Agreement_Type_CD = a.Agreement_Type_CD
LEFT OUTER JOIN (
select distinct Registration_Key, p.ServiceProvider
, 1 as served
from dbo.Encounters e
INNER JOIN dbo.CD_Provider_Xref p
ON e.Provider_CD = p.Provider_CD
where Encounter_Begin_DT between '08/01/2007' and '08/31/2007'
and Procedure_CD is not null
and Encounter_Units > 0
) as s2
ON a.Registration_Key = s2.Registration_Key
and p.ServiceProvider = s2.ServiceProvider
group by a.Registration_Key, ag.Agreement_Type_Name, p.ServiceProvider, served
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Sep 12, 2006
Hi!
Sorry for bad english, I'm from Brazil.
In microsoft.public.sqlserver.ce haven't found a way to improve performance
of this query. Thanks for any help or reply!
This used to take almost 6 min !!! With index on E.Produto now takes about 30 sec...
1,909 row table
Ipaq 1950 - Samsung 300 Mhz - 32 MB RAM - Windows Mobile 5.0 - SQL CE
2.0
PK (all multiple columns) - tables:
Lotes - pk(Empresa, Lote, Contagem, Produto)
Contagem - pk(Empresa, Lote, Contagem, Produto)
Produtos - pk(Codigo) // this field also is FK <=> Produto in all other
tables
Estoque - pk(Empresa, Ordem, Produto)
Part of my VB.NET code with SQL:
sql_grd_inv = "SELECT L.Empresa, L.Lote, L.Contagem, L.Produto" _
& ", P.Unidade, P.Descr, P.Ref, P.Embgem, P.Marca" _
& ", Sum(CASE WHEN E.Estoque IS NULL THEN 0 ELSE E.Estoque END)" _
& "AS SomaEstoque, C.Qtde" _
& " FROM (" _
& "(Lotes L " _
& "LEFT JOIN Contagem C ON (L.Empresa = C.Empresa) " _
& "AND (L.Lote = C.Lote) AND (L.Contagem = C.Contagem) " _
& "AND (L.Produto = C.Produto)" _
& ") " _
& "LEFT JOIN Estoque E ON (L.Empresa = E.Empresa) " _
& "AND (L.Produto = E.Produto)" _
& ") " _
& "INNER JOIN Produtos P ON L.Produto = P.Codigo " _
& "GROUP BY L.Empresa, L.Lote, L.Contagem, L.Produto" _
& ", P.Unidade, P.Descr, P.Ref, P.Embgem, P.Marca, C.Qtde " _
& "HAVING (L.Empresa='" & IncEmpresa & "') " _
& "AND (L.Lote='" & Cbo_Lote_Pnl_Invent.Text & "') AND (L.Contagem='" _
& Cbo_Cont_Pnl_Invent.Text & "') " _
& "UNION " _
& "SELECT " _
& "C.Empresa, C.Lote, C.Contagem, C.Produto" _
& ", P.Unidade, P.Descr, P.Ref, P.Embgem, P.Marca" _
& ", Sum(CASE WHEN E.Estoque IS NULL THEN 0 ELSE E.Estoque END)" _
& "AS SomaEstoque, C.Qtde" _
& " FROM (" _
& "(Contagem C " _
& "LEFT JOIN Lotes L ON (C.Empresa = L.Empresa) " _
& "AND (C.Lote = L.Lote) AND (C.Contagem = L.Contagem) " _
& "AND (C.Produto = L.Produto)" _
& ") " _
& "LEFT JOIN Estoque E ON (C.Empresa = E.Empresa) " _
& "AND (C.Produto = E.Produto)" _
& ") " _
& "INNER JOIN Produtos P ON C.Produto = P.Codigo " _
& "GROUP BY C.Empresa, C.Lote, C.Contagem, C.Produto" _
& ", P.Unidade, P.Descr, P.Ref, P.Embgem, P.Marca, C.Qtde" _
& ", L.Empresa, L.Lote, L.Contagem, L.Produto " _
& "HAVING (L.Empresa Is Null) AND (L.Lote Is Null) " _
& "AND (L.Contagem Is Null) AND (L.Produto Is Null) " _
& "AND (C.Empresa='" & IncEmpresa & "') " _
& "AND (C.Lote='" & Cbo_Lote_Pnl_Invent.Text & "') AND (C.Contagem='" _
& Cbo_Cont_Pnl_Invent.Text & "') "
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Apr 26, 2006
Hello SQL Gurus,
From the query below, I am using 2 TOP functions to return the desired row. I am wondering if someone can shed some light on how to AVOID using 2 TOP statements and combine into just one select query?
select TOP 1 * from (select TOP 2 Num from A order by Num) X order by Num desc
Truly Appreciate your help as this performance issue has been bugging in my head for quite some time...
Sincerely,
-Lawrence
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Apr 16, 2008
Hi,
I am wondering if someone can clear my mind about a performance doubt.
What performs best using inner or left joins... I filter my data in the ON clauses or in the WHERE clauses...
Example 1:
FROM TABLE_A A INNER JOIN TABLE_B B ON A.ID = B.ID AND A.ID IN (@IDS)
Example 2:
FROM TABLE_A A INNER JOIN TABLE_B B ON A.ID = B.ID
WHERE A.ID IN (@IDS)
Consider that table A and B can contain large sets of data.
Best Regards,
Luis Simões
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Mar 14, 2008
I usually am all over answering these kinds of questions, but while I continue to work on this issue, maybe someone here can lend me a hand. A vendor application we run, stores metadata about backup blobs stored on a NAS device. The app basically backs up select folders on 1400 remote computers in the back office of our stores, and stores this on a NAS, while maintaining metadata about the BLOBs in SQL Server so that they can push recovery of the data back to the original store it came from. The database is roughly 80GB in size and has a single file group and is on its own dedicated LUN. It uses TempDB heavily, and this is not something that I can change, but TempDB is on a different disk array.
Today I spent hours on a conference call with them looking at a specific stored procedure that is used to clean up the records in the database after a BLOB file is deleted. A single BLOB file can have millions of related records in the database. There is a LEFT JOIN in the code that is against a table with 150 million + rows of data in it. The table size is fairly small, only 5 GB of data, but the LEFT JOIN spools 2.4GB of data to a Hash Match. It seems to me like the left join can't be removed, but I don't get how all of this works, because I didn't write the application. It is an INDEX SCAN. I can't seem to eliminate it. Is there anything I can do to help this thing out?
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May 7, 2007
I am attempting to get a better understanding of why my SQL 2005 setup when running a simple select statement on a large table is displaying very low IO in performance monitor. If i run a single Select * From testtable i see 4mbsec transfer and Disk readssec is around 8-9. This particular table is sitting on a single U320 10k drive so i expecting to see far more substantial IO. Does anyone have any information on how IO is consumed using different SQL operations so i can obtain a better understanding?
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Jan 21, 2008
So I am experimenting with upgrading a Windows Mobile application from .NETCF 2.0 to .NETCF3.5, along with moving my SQL 2005 Compact to SQL Compact 3.5. I have a database that I upgraded using the recommended methods (creating a datasource in VS2008, opening the SQL 2005 Compact .sdf file and allowing the tool to upgrade to SQL Compact 3.5). On the device (Dell Axim x51), with the .SDF files on an SD Card, the query, when executed against the SQL 2005 Compact database file, takes 1.5 seconds, but takes 1min41sec to execute on the SQL Compact 3.5 database.
This is a fairly simple query, with an inner join (using about 4 inner join constraints), a where clause (over about 3 things), and an order by clause. The execution plan for the SQL Compact 3.5 query shows index seeks (one consuming 2% and the other consuming 0%, with the inner join using 98%). The database files are on the order of 90MB.
Can anyone offer any suggestion why the SQL Compact 3.5 query performance would be so much worse than the SQL 2005 Compact performance?
Thanks,
Matthew Belk
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Apr 27, 2006
The below query seems to be very slow :
select distinct a.* from test a inner join test1 b on b.col1 = a.col1
inner join test2 c on c.col2 = a.col2 where exists (select NULL from
test3 d where (d.col3 = a.col3 or a.col3 is null))
All the columns involved in the WHERE clause and JOIN conditions have
index. Is there any alternative available for the above which can
increase the performance ?
Please advice,
Thanks,
Smitha
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Sep 15, 2001
I'm looking for a query that can "batch" update one table from another. For example, say there are fields on both tables like this:
KeyField
Value1
Value2
Value3
The two tables will match on "KeyField". I would like to write one SQL query that will update the "Value" fields in Table1 with the data from Table2 when there is a match.
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