Hi,
We know cursors are evil, use lot of memory, adds up tempdb activity, not scalable, hinders concurrency etc...Say if I replace 10 heavily used cursors in OLTP system with while loops how much do I gain if any and how can I measure that. How can I convince my code review DBA to make this change? Does this change help the server?
Hi all,
I have a bit of a challenging on my hands with this,
i have a result set in a table which i am trying to iterate through the rows one by one i.e
Values
Values Dates
1.10
1.20
1.30
1.40
2006-03-31 00:00:00.000
2006-06-30 00:00:00.000
2006-09-30 00:00:00.000
2006-12-31 00:00:00.000
go to each row get the value and the date perform some calculation with the value and the date and insert it into another table(which sounds easy enough) my problem is how do i iterate through the result set one by one without using a cursor or a while loop?
do i have any other options at all?
Working on some new code, I'm coming across WHILE loops used instead ofcursors. I was curious if anyone had any stats on how the speed ofdoing this compares to the speed of a cursor. I typically avoidcursors for performance sake, but I'm not sure how this avoids thespeed hit of a cursor, since it's doing essentially the same thing.Many thanks.
View 4 Replies View Related
Hello
I have a question
How is foreach loop container - foreach ADO enumerator performace in SSIS package compares to use of cursors in stored procedures
Is there any articles comparing them
I understand a lot of factors can affect the performance, however what is expected performance for the foreach ADO enumerator loop for large dataset. What is Microsoft recommendation for that - recommended - not recommended (using large datasets - over million records)
Thank you
Arminr Bell
difference between FOR LOOP and FOREACH LOOP with example(if possible) in SSIS.
View 4 Replies View RelatedI have a table with RowID(identity). I need to loop though the table using RowID(not using a cursor). Please help me.
Thanks
I have a foreach loop that is supposed to loop through a recordset, however it doesn't loop. It just repeats the same row, row after row.
I would like to look into the recordset variable but I can't because it is a COM object and the ADODB namespace is not available in the script task.
Any solution to this? anyone experienced anything similar
I have a table called Tbltimes in an access database that consists of the following fields:
empnum, empname, Tin, Tout, Thrs
what I would like to do is populate a grid view the a select statement that does the following.
display each empname and empnum in a gridview returning only unique values. this part is easy enough. in addition to these values i would also like to count up all the Thrs for each empname and display that sum in the gridview as well. Below is a little better picture of what I€™m trying to accomplish.
Tbltimes
|empnum | empname | Tin | Tout | Thrs |
| 1 | john | 2:00PM | 3:00PM |1hr |
| 1 | john | 2:00PM | 3:00PM | 1hr |
| 2 | joe | 1:00PM | 6:00PM | 5hr |
GridView1
| 1 | John | 2hrs |
| 2 | Joe | 5hrs |
im using VWD 2005 for this project and im at a loss as to how to accomplish these results. if someone could just point me in the right direction i could find some material and do the reading.
I have source and destination table names in the database(one table) and I need to read the source and destination tables one by one...
My Lookp table is like the following...
Srn srctable desttable
1 SRC1 DEST1
2 SRC2 DEST2
3 SRC3 DEST3
Now I want one package to load from source to destination.. how do I do it.. I dont know how to use....
How do I run the pacakge for each of the rows... ..............................
Hello,
Can anyone direct me a good article that is about why we should try avoiding using cursors and what are the alternatives?
can we call cursors from asp.net as we can call stored procedures from asp.net.
Hi,
I'm writting a stored procedure to insert new rows into a table, but I need to loop through an exsiting table and create a new record for every row in the old table. So I think what I'm needing to use is a cursor, but I've never worked with cursors before, and I just want to check that I have the right idea on what they are used for and if what I have so far looks ok.
This what I have so far, the StoreFees table only has 5 rows:
DECLARE @StoreFee as smallmoney
DECLARE @StoreLineID as int
DECLARE MyStoreFees CURSOR
FORWARD_ONLY
FOR
SELECT LineId, StoreFee FROM StoreFees ORDER BY StoreFee
OPEN MyStoreFees
FETCH NEXT FROM MyStoreFees
INTO @StoreLineId, @StoreFee
--Do my Inserts into other tables
INSERT INTO OtherTable (...,...,.., @StoreFee)
...
...
-- Done working with that row
CLOSE MyStoreFees
I am trying to pull the data via fetching rows into a variable.
Begin
Fetch Next Into @temp...
Select @MainVariable = @MainVariable + @temp < @temp doesn't refresh with next fetch)
Print @temp < this works fine and returns the value for each fetch
End
I can print @temp and the data returns fine, but when I try to cancantenate with the above select, it doesn't refresh @temp wit the column in the table.
Any ideas?
DotNetNow
I have two procedures. One works well, and the other has a small glitch I cannot figure out. I have placed >>>> at the place where the problem is occuring.
The first procedure, which is working great, is applying a stored procedure to many servers (remote procedure call), but is also polling the local server via a linked server connection. This way, all servers are polled equally.
The second procedure is actually using a SELECT statment to query a system table. This procedure works well on all servers except the local one. I get this error message:
Server: Msg 3910, Level 16, State 1, Line 1
Transaction context in use by another session.
[OLE/DB provider returned message: Unspecified error]
There seems to be a connection issue. Can someone help me work around this?
Thank you,
Neal
FIRST PROCEDURE (this one works perfectly):
truncate table dbidname
CREATE TABLE ##dbtemp ( dbname VarChar(50),
dbsize varchar (25),
dbownervarchar(50),
dbid smallint,
createdate datetime,
statusvarchar(75) )
declare@servernamevarchar(50)
declare dbupdate cursor
global
for
select servername from sqlservers where status = 'a'
open dbupdate
fetch next from dbupdate into @servername
while @@fetch_status = 0
begin
print @servername
EXEC sp_addlinkedserver @servername, 'SQL Server'
>>>INSERT INTO ##dbtemp
>>>exec (@servername + '.master..sp_helpdb')
alter table dbidname alter column sqlservers_id int null
insert into dbidname (dbsystemid, dbname)
select dbid, dbname from ##dbtemp
update dbidname set sqlservers_id = sqlservers.sqlservers_id from sqlservers where @servername = sqlservers.servername and
dbidname.sqlservers_id is null
update dbidname set whenupdate = getdate()
alter table dbidname alter column sqlservers_id int not null
exec sp_dropserver @servername
delete ##dbtemp
fetch next from dbupdate into @servername
end
close dbupdate
deallocate dbupdate
drop table ##dbtemp
exec spal_db_files_update
SECOND PROCEDURE (see >>>> to note problem area):
truncate table dbidname
CREATE TABLE ##dbtemp ( dbname VarChar(50),
dbsize varchar (25),
dbownervarchar(50),
dbid smallint,
createdate datetime,
statusvarchar(75) )
declare@servernamevarchar(50)
declare dbupdate cursor
global
for
select servername from sqlservers where status = 'a'
open dbupdate
fetch next from dbupdate into @servername
while @@fetch_status = 0
begin
print @servername
EXEC sp_addlinkedserver @servername, 'SQL Server'
>>>>INSERT INTO ##dbtemp
>>>>exec (@servername + '.master..sp_helpdb')
alter table dbidname alter column sqlservers_id int null
insert into dbidname (dbsystemid, dbname)
select dbid, dbname from ##dbtemp
update dbidname set sqlservers_id = sqlservers.sqlservers_id from sqlservers where @servername = sqlservers.servername and
dbidname.sqlservers_id is null
update dbidname set whenupdate = getdate()
alter table dbidname alter column sqlservers_id int not null
exec sp_dropserver @servername
delete ##dbtemp
fetch next from dbupdate into @servername
end
close dbupdate
deallocate dbupdate
drop table ##dbtemp
I am receiving this error when running my cursor:
Error Messages...
Server: Msg 16933, Level 16, State 1, Line 0
The cursor does not include the table being modified.
The statement has been terminated.
Server: Msg 16933, Level 16, State 1, Line 5 (this message repeats)...
The cursor does not include the table being modified.
The statement has been terminated.
query:
declare cursor_test CURSOR for
select emp_ssn, effective_date1 from temp_employee_benefit_load
open cursor_test
declare @ssn char(9), @process_date char(8)
fetch next from cursor_test into @ssn, @process_date
while (@@fetch_status=0)
update test_cursor
set ssn = @ssn, process_date = @process_date
where current of cursor_test
fetch next from cursor_test into @ssn, @process_date
close cursor_test
deallocate cursor_test
Any help is appreciated:
Thanks,
I have stored procedure in that I am using a cursor to fetch the row by row.
cursor is fetching 75000 records so that the procedure is taking long time.
Is there any way to replace the cursor to fetch the records row by row.
He needed.
Ranch
Please help resolve a problem (and debate!).
We have an app using VB with Access as the front end to SQL. SQL statments were built and sent
directly to the server obtaining set-oriented results. Response was fair.
We have a new app developed by an "expert" using VB & Interdev that was to be ported for use on
the internet. The app was designed using the same logic to build the SQL statements, but it is also
using cursors to retrieve all data. RESPONSE IS TERRIBLE!
The designer says that to access SQL over the Web, cursor use is a MUST!
True? Not True?
If true, and I am stuck with an app using cursors, any basic suggestions on where to look to improve
response time?
Thanks for any input.
FJ
Hi,
I am using SQL Server 6.5 and I have a VB routine that updates a field in a tble so it can be used in a primary key. This is run after input of data using bcp. I have noticed on several posts re: using cursors to move through a recordset and was wondering if I could use this functionality to replace my VB routine. I checked the archives and found several messages but I am not sure where to start. My VB routine is:
I first would query the data to return all rows where the value of R08SegmentValue= Null. Then I move through the resultset changing the value of the field R08Segments.
***********************Start of VB Code****************
'Set initial value for sTReportHeaderIdx
With rs1
sTReportHeaderIdx = !ReportIdx & !HeaderIdx
sPReportHeaderIdx = sTReportHeaderIdx
End With
bCount = 1
'loop through rs and when streportheaderidx changes reset bCount to 1
'otherwise increment bcount by 1 and write to field R08SegmentValue
Do While rs1.EOF = False And blnContinue = True
DoEvents
Do While sPReportHeaderIdx = sTReportHeaderIdx
With rs1
.Edit
!R08SegmentValue = bCount
.Update
bCount = bCount + 1
sPReportHeaderIdx = sTReportHeaderIdx
.MoveNext
If Not rs1.EOF Then sTReportHeaderIdx = !ReportIdx & !HeaderIdx
End With
Loop
sPReportHeaderIdx = sTReportHeaderIdx
bCount = 1
Loop
In the end my data should look like
ReportIdx HeaderIdx R08SegmentValue
1 1 1
1 1 2
2 1 1
2 1 2
2 1 3
3 1 1
3 1 2
3 1 3
1 2 1
1 2 2
1 2 3
etc..
Can this be done via an sp? How would I go about writing something like this?
Thanks in advance...any assistance you could provide would be appreciated!
Kevin
I hope someone can help me with this, as BOL didn't get me the answer I am looking for.
I want to write an update step that will transform the following:
1 abc
1 def
2 lmn
3 rst
4 tuv
4 xyz
4 jkl
5 pqr
into this:
1 abc,def
2 lmn
3 rst
4 tuv,xyz,jkl
5 pqr
In other words, I want to concatenate multiple instances into 1 record per row, but I am not familiar with working with cursors or loops.
Thanks in advance!
bv
According go textbooks and T-SQL developers experience - using cursors is not recommended, more over they say: avoid cursors where it's possible.
Could someone please recommend any other way to go through the recordset(resultset) forward and backward to perform some search or calculations, if there are a specific requirement for not using front-end tools such as VB or MS Access(please don't ask why), other words - all the work must be performed in T-SQL stored procedure.
Thanks
Hi
I defined a cursor and executed it...but now i exactly forgot what select statement i had run in the cursor..(forgot the columns that i am extracting )
how do I view the contents of the cursor ?
I have a stored proc that merges records from an undeduped table to a deduped table. It is running really slowly. Merging 70 million records against a deduped 70 million is taking 115 hours and counting on decent hardware. Very slow.
I suspect there is significant room for optimization here. Some of my ideas:
- Write/update back to the cursor rather than executing separate UPDATE statements.
- Try a dynamic cursor instead of a READ ONLY cursor.
- Dump new elements to a separate table or a file and then do a single large INSERT.
Anyone else think any of these ideas will work? Can anyone think of something better?
BTW, I've tried to replaced the procedural cursor code with set based UPDATES/INSERTS but the short version of the story is that that route just didn't pan out. I know that is very common optimization advice.
I've made minor simplifications to the code:
- Took out code to handle last line
- Took out progress logging code
- Removed some DECLARE statements. These are needed to run but it should be obvious what they were supposed to be.
Trying to understand cursors a little better, found this in one of the dbs I inherited. Just trying ot figure out why they put it there cause no one else knows anything about it.
DECLARE [TM #] CURSOR
FOR SELECT * FROM [2004 TERMS];
nevermind forget I asked thanks anyways
View 11 Replies View RelatedThese guys I work with have some sql scripts they run over night and they bog down the server and the machine will be gummed up in the morning etc..
Well, I finally looked at this processing and the culprit is cursors. And cursors within cursors. I would like to just get some opinions about what would be more processor efficient so I can send my boss a link to this thread.
Using a cursors to pull records and update them.
vs
Create script using a scripting language that pulls the records through ADO, loops through them and performs updates as necessary using update statements and the like.
Be nice. I have to work with these guys.
In what situations would you use a cursor over a t-SQL update/select statement
View 3 Replies View RelatedHey guys
I have heard cursors are not the way to go. But I am wondering if/how to get out of a situation that I am using a cursor in...in order to make my stored proc run more effieciently.
I am quite novice in my abilities and I am completely stumped on how to get around using them.
As far as INSERTs go, I think I can work around that, but how would I write UPDATE statements for all lines of a table to say pull a key from another table to reference them together?
I usually make my SELECT statement in the cursor, then update against the criteria from the SELECT statement. Now this is quite a slow process when I am updating 100K records.
Any help or pointers or a link to a good tutorial would be woderful.
Thanks
tibor
declare BadRecords cursor dynamic for select lngZipCodeID
from ZipCodes where lngZipCode=@ZipCode and lngZipCodeID<>@NewZipID
/* this is the syntax in Sybase
open BadRecords;
BadRecordsLoop: loop
fetch next BadRecords into BadID;
if sqlstate<>0 then
leave BadRecordsLoop
end if
*/
I have to convert it to sql , I m just checking whether my syntax is correct or not
open BadRecords
while @@fetch_status = 0
begin
set @BadId = fetch next BadRecords
if @@Error = 0
end
I have doubt in my syntax. Can you help me out in this?
Thx
I have a requirement to check a value which MUST be unique forever even if it is removed and readded.I have created a seperate table to maintain this value.
Without using a cursor how would I be able to append a duplicate base value (i.e. smith.j@here.now) with the next sequential value (i.e. smith.j02@here.now)
Any takers?
Oh ya, These values are not manually entered but populated through a DTS script. The existing values are repopulated from historic tables and new entries are added automatically. Initially the values would be populated without a number but a number needs to be generated on duplicates.
Could not complete cursor operation because the table schema changed after the cursor was declared.
View 5 Replies View RelatedI have a Stored Procedure that show RentArrears for a tenant only
eg Execute RentArrears '88' where 88 is the tenantID
Now I want to execute it for other tenants, I want think of using Cursors to loop thru tenent table , but everybody is frowning at it, what other method can I use to loop thru tenant so as to use my stored procedure
Thanks
If it is that easy, everybody will be doing it
Can someone tell me what is wrong with this code?
I just want to get the account_number field from the accounts table and put it in the results table. Let me clarify, there are over 500 rows in the accounts table and I want to loop through those while setting the accounts.account_number = results.account_number.
declare @account nvarchar
DECLARE Accounts_Cursor CURSOR FOR
SELECT account_number FROM accounts
OPEN accounts_Cursor
FETCH NEXT FROM accounts_Cursor into @account
WHILE @@FETCH_STATUS = 0
BEGIN
update results
set account_number = @account
FETCH NEXT FROM accounts_Cursor into @account
END
CLOSE accounts_Cursor
DEALLOCATE accounts_Cursor
declare @sal char(50)
DECLARE Employee_Cursor1 CURSOR static for
SELECT salary
FROM test2
OPEN Employee_Cursor1
FETCH FROM Employee_Cursor1 into @sal
WHILE @@FETCH_STATUS = 0
BEGIN
FETCH NEXT FROM Employee_Cursor1 into @sal
PRINT 'this is NOT the desired output which i wanted from so long :'+@sal
END
CLOSE Employee_Cursor1
DEALLOCATE Employee_Cursor1
Rahul