I've been working as a .NET developer for many years. However, my educational background isn't in IT at all, so I occasionally find that there are big gaps in my knowledge when I'm called on to do certain things.
My current role is the first one I've had where the efficiency of my database calls has needed to be top-notch. Most of my previous posts have been in building intranet functionality for medium-sized companies so it's just not been an issue and my fairly basic level of SQL knowledge has been enough to get me by.
However, I'm increasingly finding I'm needing to look stuff up, ask for help and so forth and I'm not at all sure that what I'm putting out is up to scratch. I have three main areas of concern:
1) The developers here seem to like doing a lot of the "work" of data sorting and manipulation in SQL whereas I'd previously have just grabbed the whole table and done the manipulation in .NET. I'm finding building my complex queries is just doing my head in - I'm just not used to "thinking" in the way that SQL requires which seems very different from procedural programming.
2) A lot gets said about properly indexing tables for maximum efficiency. I know what an index is and vaguely what it does, but the means of applying them to ensure the best performance is pretty much beyond me.
3) In the same manner I'm now having to worry a lot more about performance issues in my database design. I now the five normal forms and so on, but is there anything else here I need to do to maximise performance?
What I'm asking, really, is whether anyone can recommend a good source for SQL knowledge (book, site, whatever) that specifically focuses on my first problem - it'll teach me the proper way to structure my queries and think about them properly so that they don't look so damn impenetrable. It then needs to go on and address my other issues.
Dear Friends, please suggest me the best book to gain sound knowledge in DBA concepts as well as writing in sub queries, complex queries as well as inner queries.
I am not an expert in either SSIS or VFP technology but know enough to get my way round. One anomaly I did discover I thought was worth sharing for all those concerned with getting large amounts of data out of VFP in as short a time as possible. When you search for performance tips in relation to SSIS the advice is to never use select table or view from data access mode list in ole db source as this effectively translates to select * from table and I've never come across anything to contradict this €“ well I am and let me explain why:
When you use SQL command as data access mode in ole db source (where ole db source is foxpro dbc) and you write out select column1, column 2 etc etc from table a etc etc and then connect that to a destination (in my case ole db destination) the SSIS task spends ages stuck on Pre-execute before anything happens (the bigger the fox tbl the longer the wait). What is happening behind scenes is that the foxpro engine (assuming its foxpro engine and not sql engine €“ either way don€™t think it matters too much) is executing the sql command and then writing results to a tmp (temp) file on your local temp folder €“ (in my case : C:Documents and SettingsautologinLocal SettingsTemp1). These files take up gigs of space and it is only when this process is complete does the SSIS task actually finish the Pre-execute and start the data transfer process. I couldn€™t understand a) why my packages were stuck on pre-execute for such long times? and b) why were the tmp files being created and why they were soo big?
If you change from SQL command in source to Table or view and then select your table from list the SSIS task when executed kicks off immediately and doesn€™t get stuck on pre-execute nor create any tmp files €“ so you save time and disk space. The difference in time is immense and if like me you were really frustrated with poor performance when extracting from VFP now you know why.
Btw maybe this does not apply to all versions of VFP but it certainly does to v7.
Any recommendations for good advanced t-sql books/articles? I find myself involved with writing increasingly more complex queries and after spending a few hours on some, and then searching on this site for potential answers/help, I am wondering if there might be some good books on creating more advanced/complex t-sql for real world scenarios.
I am loosing my mind on this one. I select info from a database. I then take that selected info, and select info from another table based on that. Straight forward. The CompanyKey attached to my username is 7 which displays in the ReaderResults.Text. I the following line: selectSQL2 = "SELECT * FROM Company WHERE companyKey = ('" + CompanyKey + "')"
I can change it to:
selectSQL2 = "SELECT * FROM Company_Membership WHERE companyKey = 7 "
and it works. I have no idea what is going on. Dissapearing string? Here is the code: Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load 'Database ConnectionDim con As New SqlConnection("Data Source = .SQLExpress;integrated security=true;attachdbfilename=|DataDirectory|ASPNETDB.mdf;user instance=true") 'Job1 InfoDim currentUserID currentUserID = Context.User.Identity.Name.ToString() Label1.Text = currentUserID Dim selectSQL1 As String selectSQL1 = "SELECT companyKey FROM Company WHERE UserID = ('" + currentUserID + "')"Dim cmd1 As New SqlCommand(selectSQL1, con) Dim reader As SqlDataReaderDim CompanyKey 'Job2 Info Dim selectSQL2 As String selectSQL2 = "SELECT * FROM Company WHERE companyKey = ('" + CompanyKey + "')"Dim cmd2 As New SqlCommand(selectSQL2, con) 'Job1 Select Try con.Open() reader = cmd1.ExecuteReader()Do While reader.Read() CompanyKey = reader("CompanyKey").ToString() Loop reader.Close()Catch err As Exception ReaderError.Text = "Error selecting record." ReaderError.Text &= err.Message Finally ReaderResults.Text = CompanyKey con.Close() End Try 'Job2 Select Try con.Open() reader = cmd2.ExecuteReader() GridView1.DataSource = reader GridView1.DataBind() reader.Close()Catch err As Exception ReaderError.Text = "Error selecting record." ReaderError.Text &= err.Message Finally ReaderResults.Text = CompanyKey con.Close() End Try
Hello everyone... i am new to Structured Query Language. I am learning it for the past 6 months form a book by myself. I don't have a teacher available to me. Now when i have finished that with all of the exercises completed. i want to make sure what i've learned is i've really learned it. the problem is that there is no such organization here that i join and have some hand on practical. So now i am asking u guys to help me. Tell me some way so that i make sure of whatever knowledge i have about SQL.
I do a lot of hiring for my company and a lot of the people I interviewsay that they are experts at SQL queries, but when I give them somethingsimple just beyond the typical SELECT type of queries, they choke.For example I have a table that looks like this:PK_ID - primary keyPARENT_ID - a FK to another row in the same tableThis essentially is a tree structure. I will ask interviewees to writea query that will return all the rows that have 2 direct children. Noone knows how to do this.I don't get it. I have done queries which boggle the mind and they arefar more complex than this.Am I asking too much?--* Don VaillancourtDirector of Software Development**WEB IMPACT INC.*phone: 416-815-2000 ext. 245fax: 416-815-2001email: Join Bytes! <mailto:donv@webimpact.com>web: http://www.web-impact.com/ This email message is intended only for the addressee(s)and contains information that may be confidential and/orcopyright. If you are not the intended recipient pleasenotify the sender by reply email and immediately deletethis email. Use, disclosure or reproduction of this emailby anyone other than the intended recipient(s) is strictlyprohibited. No representation is made that this email orany attachments are free of viruses. Virus scanning isrecommended and is the responsibility of the recipient./
My company asked me to do a tech interview on a potential contractor for a three month assignment writing SQL Server stored procedures.
I have some things I can ask him to test his qualifications, such as cross-tab query design, UDF usage, running total queries, select first 'N' queries, Primary Keys vs Clustered Indexes, etc...
I was curious what questions other people might ask in order to assess a person's skill. Remember that this is SQL programming only, not admin stuff, and I want to ask questions with a range of difficulty from easy to head-cracker.
I am having a puzzling problem with a DTS package in SQL 2000 that uses a combination of "Execute Process Tasks" and "ActiveX Script Tasks." The issue occurs with one of (the second) the ActiveX Script Task. The script invokes a COM object that was written in C#. This COM object connects to the database and writes a record set and then calls a stored procedure. When I run this step individually, everything works fine. When I run it as part of the package, the record set is being written but the stored procedure is not invoked (SQL Profile confirms this).
I haven't really begun a serious attempt to troubleshoot the problem, though I have played around with the Transactions and OLE DB properties of the DTS Package.
Any suggestions as to why the behavior might be different, or some straightforward tips on troubleshooting would be appreciated. I have access to the COM component source.
I dont know where to put this thread, I just wanna ask a question..actually what is happen when subscription synchronized the publications among IIS process.. (SQLMobile)
I don't have any knowledge about SQL Server at all... I wanna know:
1. What is SQL Server? 2. Have SQL Server something to do with databases and Microsoft Access to do? 3. What is the link between Visual C++ Express Edition and SQL Server Express Edition? 4. Where on the web can I learn (tutorials) how to use SQL Server Express Edition?
Greetings,I have to admit that I'm still a beginner in the database field, but I'mactively studying, and this is why I will be utterly grateful for theproper, accurate, and wise guidance to the right direction or specificpaths of database studies.I simply want to make my first major database project a "personalknowledge database" or a "personal encyclopedia", so to speak. By this Imean that I want to gather diverse, multi-format bits of knowledge intoa single database divided into major categories, sub-categories, and soon. For example, I want to scan collected articles from newspapers &magazine and save them as images, type hand-written notes into thecomputer and save them as MS Word or Text files, save audio files withsearchable keywords, even save searchable MS OneNote audio & text files,all into directories & sub-directories. Then I want to be able to searchall these files for specific words or subjects; sort them according todate, subject, etc; update, add to or append, edit, or even cut & paste(within) any of those records in the database, which rely on easilycustomizable formats like text & images (in contrast with audio files orOneNote files, for example).I also want to prevent wasting time in the future, by avoidingrepetitive, same-keywords typing for every non-text new entry, like animage or audio file, by having a customizable keyword list open (byright clicking for example), where one could mark all the relevantkeywords for the picture or audio file. Also have a short descriptionfor each one of those entries when needed. And I want to be able to addslick, good-looking graphics to the interface of the database and theforms of the records.Basically, my priorities include: saving time filling the database withknowledge, quickly & accurately finding the future targets of anysearch, presenting the search results in a highly comprehensible &organized form, and a good looking interface & forms for every entry,which are pleasing to the eye and encouraging to study.I already use graphics applications for the "looks" part. So my questionis: what are the technologies or applications that I should learn byheart and use in order to design such a database in the best way? WouldMS Access alone do it all for me? Or should I learn other technologies?I'll be grateful for anyone taking the time to help. Thanks.Sincerely,Yasso"Claiming that God does not exist because there are people suffering anddying is like saying that barbers do not exist because there are peoplewith long hair! Truth is: they suffer because they did not find God ordo not go to Him, just like the others did not find a barber or do notgo to one."*** Sent via Developersdex http://www.developersdex.com ***Don't just participate in USENET...get rewarded for it!
Hello, I've been trying for a couple of days now with the following problem in SQL Ive a table called tblRresults that has the following Date - just a regular date OfficeLocation - just a unique id such as a zip code SampleType - contains things like wall, floor, beam SampleResult - "Detected" or "NotDetected" When populated the table can look like 12/12/05 99505 Wall Detected 12/12/05 99505 Wall NotDetected 10/04/05 99211 Beam Detected 10/04/05 99211 Beam Detected 10/04/05 99111 Floor NotDetected 10/04/05 99111 Floor NotDetected What I want is (I guess) a crosstab query that produces the following Date Location SampleType CountDetected CountNotDetected 12/12/05 99505 Wall 1 1 10/04/05 99211 Beam 2 0 (or null would be ok) 10/04/05 99111 Floor 0 2 Any help gratefully accepted, this has been driving me mental! thanks
I have the following SQL, which works but I think it can be done simplier. I seem to have to group it by multiple columns, but I am sure there must be a way of grouping the results by a single column. Any Ideas?
Code:
SELECT count(order_items.order_id) as treenum, orders.order_id, orders.order_date, orders.cust_order, orders.del_date, orders.confirmed, orders.del_addr FROM orders, order_items WHERE orders.order_id = order_items.order_id GROUP by orders.order_id, orders.order_date , orders.cust_order, orders.del_date, orders.confirmed, orders.del_addr ORDER BY orders.order_id DESC
I have four different transactions such as below and I do one insert and one update in each transaction and it seem it is slow and creates deadlock with the user interface.
These transactions are performed against the tables that users are accessing with another user interface. I have following two questions:
1. T2.TextField1 and TextField2 = @TextField2 are Ok, Nok fields so I did not put index since only two distinct values. Should I put indexes on these fields?
2. Can I make this transaction let user interface do its task in case accessing the same rows, I can start transaction again but I do not want users get disturbed? .
BEGIN TRANSACTION pTrans BEGIN INSERT INTO T1 (fields) SELECT (fields) FROM T2 INNER JOIN View1 ON T2.TrID = View1.MyTableID WHERE (T2.TextField1 = @TrType AND T2.TextField2 = @TextField2)
UPDATE T2 SET TextField2 = 'Ok', TextField2Date=@MyRunDateTime FROM T2 WHERE (TextField1 = @TrType AND TextField2 = @TextField2)
IF @@ERROR <> 0 BEGIN rollback transaction pTrans return(-1) END ELSE BEGIN commit transaction pTrans END END
I have a pretty good db server with four CPUs, it has not any other loads on it, but the following query takes 4ms to return. I use the syscolumns this way quite often, I am not sure why it takes it that long to return, any idea? select 'master',id,colid,name,xtype,length,xprec,xscale,status from [ablestatic].[dbo].syscolumns where id=(select id from [ablestatic].[dbo].sysobjects where name='link_data_ezregs')
hi, have a nice day to all , can some expert here point out what are the do and don't when we writing query ? ie:should we create many view as handler to get data? when should we use store procedure and trigger ? and so on
i seeking the way to improve my sql skill, can someone suggest some reference site or material or book as well ?
I wrote the following function a few years ago - before I learned about SQL's PATINDEX function. It might be possible to check for a valid email address syntax with a single PATINDEX string which could replace the entire body of hte function below.
Is anyone is interested in taking a crack at it?
Signed... lazy Sam
CREATE FUNCTION dbo.EmailIsValid (@Email varchar (100)) /* RETURN 1 if @Email contains a valid email address syntax, ELSE RETURN 0 */
RETURNS BIT AS BEGIN DECLARE @atpos int, @dotpos int
SET @Email = LTRIM(RTRIM(IsNull(@Email, ''))) -- remove leading and trailing blanks
IF LEN(@Email) = 0 RETURN(0) -- nothing to validate
SET @atpos = charindex('@',@Email) -- position of first (hopefully only) @
IF @atpos <= 1 OR @atpos = LEN(@Email) RETURN(0) -- @ is neither 1st or last or missing
IF CHARINDEX('@', @email, @atpos+1) > 0 RETURN(0) -- Two @s are illegal
IF CHARINDEX(' ',@Email) > 0 RETURN(0) -- Embedded blanks are illegal
SET @dotpos = CHARINDEX('.',REVERSE(@Email)) -- location (from rear) of last dot
IF (@dotpos < 3) or (@dotpos > 4) or (LEN(@Email) - @dotpos) < @atpos RETURN (0) -- dot / 2 or 3 char, after @
I have this SQL query that can take too long time, up to 1 minute if table contains over 1 million rows. And if the system is very active while executing this query it can cause more delays I guess.
select distinct 'CONV 1' as Conveyour, info as Error, (select top 1 substring(timecreated, 0, 7) from log b where a.info = b.info order by timecreated asc) as Date, (select count(*) from log b where b.info = a.info) as 'Times occured' from log a where loggroup = 'CSCNV' and logtype = 4
The table name is LOG, and I retrieve 4 columns: Conveyour, Error, Date and Times occured. The point of the subqueries is to count all distinct post and to retrieve the date of the first time the pst was logged. Also, a first and last date could be specified but is left out here.
Does anyone knows how I can improve this SQL query?
I have four different transactions such as below and I do one insert and one update in each transaction and it seem it is slow and creates deadlock with the user interface.
These transactions are performed against the tables that users are accessing with another user interface. I have following two questions:
1. T2.TextField1 and TextField2 = @TextField2 are Ok, Nok fields so I did not put index since only two distinct values. Should I put indexes on these fields?
2. Can I make this transaction let user interface do its task in case accessing the same rows, I can start transaction again but I do not want users get disturbed? .
BEGIN TRANSACTION pTrans BEGIN INSERT INTO T1 (fields) SELECT (fields) FROM T2 INNER JOIN View1 ON T2.TrID = View1.MyTableID WHERE (T2.TextField1 = @TrType AND T2.TextField2 = @TextField2)
UPDATE T2 SET TextField2 = 'Ok', TextField2Date=@MyRunDateTime FROM T2 WHERE (TextField1 = @TrType AND TextField2 = @TextField2)
IF @@ERROR <> 0 BEGIN rollback transaction pTrans return(-1) END ELSE BEGIN commit transaction pTrans END END
hi in asp.net,i used sql server to store records. in a table has 1 million records,but when i update the record,it is very slowly. is "create index" helpful for "update" operation? i need help,thanks a lot.
Hi, We have a poorly performing SQL 2000 db. i have just defragged ( the HD, not indexes, these are done daily via SQL Agent) the data files of our server and have not found any improvement in response. I have now got into using SQL profiler to analyse the server performance. in the results that the trace is returning there are some huge (REALLY BIG) values for the duration and cpu values but these rows have no textdata value returned (ie it is null)
why is this? for these rows, the reads and writes columns are also high.
if these rows are what is taking the cpu's time then how can i identify what the server is doing to make any changes?
any thoughts on what other values i might trace or what action i can take to find the slow down cause?
in performance manager the processors (dual Xeons) are rarely dropping below 60%.
is there anyway to improve this statement. make it short? any input will be appreciated.
update TempAddressParsingTable set ad_unit = case
when right(rtrim(ad_str1),3) like 'apt' or right(rtrim(ad_str1),3) like 'lot' and substring(reverse(ad_str1), 4,1) in ('', ',', '.') then right(ad_str1,3)
when right(rtrim(ad_str1),4) like 'unit' or right(rtrim(ad_str1),4) like 'apt%' or right(rtrim(ad_str1),4) like 'lot%' and substring(reverse(ad_str1), 5,1) in ('', ',', '.') then right(ad_str1,4)
when right(rtrim(ad_str1),5) like 'unit%' or right(rtrim(ad_str1),5) like 'apt%%' or right(rtrim(ad_str1),5) like 'lot%%' and substring(reverse(ad_str1), 6,1) in ('', ',', '.') then right(ad_str1,5)
when right(rtrim(ad_str1),6) like 'unit%%' or right(rtrim(ad_str1),6) like 'apt%%%' or right(rtrim(ad_str1),6) like 'lot%%%' and substring(reverse(ad_str1), 7,1) in ('', ',', '.') then right(ad_str1,6)
when right(rtrim(ad_str1),7) like 'unit%%%' or right(rtrim(ad_str1),7) like 'apt%%%%' or right(rtrim(ad_str1),7) like 'lot%%%%' and substring(reverse(ad_str1), 8,1) in ('', ',', '.') then right(ad_str1,7)
when right(rtrim(ad_str1),8) like 'unit%%%%' or right(rtrim(ad_str1),8) like 'apt%%%%%' and substring(reverse(ad_str1), 9,1) in ('', ',', '.') then right(ad_str1,8)
when right(rtrim(ad_str1),9) like 'unit%%%%%' or right(rtrim(ad_str1),9) like 'apt%%%%%%' and substring(reverse(ad_str1), 10,1) in ('', ',', '.') then right(ad_str1,9)
when right(rtrim(ad_str1), 2) like '#%' and substring(reverse(ad_str1), 3, 1) in ('', ',', '.') then right(ad_str1, 2) when right(rtrim(ad_str1), 3) like '#%%' and substring(reverse(ad_str1), 4, 1) in ('', ',', '.') then right(ad_str1, 3) when right(rtrim(ad_str1), 4) like '#%%%' and substring(reverse(ad_str1), 5, 1) in ('', ',', '.') then right(ad_str1, 4) when right(rtrim(ad_str1), 5) like '#%%%%' and substring(reverse(ad_str1), 6, 1) in ('', ',', '.') then right(ad_str1, 5) else null end
Dear Experts, I'm a DBA, Working for a Product based company. We are implementing our product for a certain client of huge OLTP. our reports team is facing problem (error: all the reports are timed out).though the queries are written properly, Each query is taking some minutes of time. I've given the command DBCC DROPCLEANBUFFERS. the time immediately dropped to 10 sec.
now my question is : please suggest me the DBCC commands or any DBA related commands to improve the performance of the application for my reports team.
from your experience in SQL 2005 - do i have any free software that can help in improve performance or can help in identifying performance bottleneck. two examples of performance and help that i use usually use are the maintenance plan that do (check DB > reorganized index > rebuild index > update statics) and the second software is the SQL 2005 DASHBOARD for the reporting help. do you have any other free tools and help that you can give me for performance or any thing that i must have in my SQL 2005 servers.
I have a table called work_order which has over 1 million records and acontractor table which has over 3000 records.When i run this query ,it takes long time since its grouping bycontractor and doing multiple sub SELECTs.is there any way to improve performance of this query ??-------------------------------------------------SELECT ckey,cnam,t1.contractor_id,count(*) as tcnt,(SELECT count(*) FROM work_order t2 WHEREt1.contractor_id=t2.contractor_id and rrstm=1 and rcdt is NULL) as r1,(SELECT count(*) FROM work_order t3 WHEREt1.contractor_id=t3.contractor_id and rrstm=2 and rcdt is NULL) as r2,(SELECT count(*) FROM work_order t4 WHEREt1.contractor_id=t4.contractor_id and rrstm=3 and rcdt is NULL) as r3,SELECT count(*) FROM work_order t5 WHEREt1.contractor_id=t5.contractor_id and rrstm=4 and rcdt is NULL) as r4,(SELECT count(*) FROM work_order t6 WHEREt1.contractor_id=t6.contractor_id and rrstm=5 and rcdt is NULL) as r5,(SELECT count(*) FROM work_order t7 WHEREt1.contractor_id=t7.contractor_id and rrstm=6 and rcdt is NULL) as r6,SELECT count(*) FROM work_order t8 WHEREt1.contractor_id=t8.contractor_id and rcdt is NULL) as open_count,(SELECT count(*) FROM work_order t9 WHEREt1.contractor_id=t9.contractor_id and vendor_rec is not NULL) asAck_count,(SELECT count(*) FROM work_order t10 WHEREt1.contractor_id=t10.contractor_id and (rtyp is NULL or rtyp<>'R') andrcdt is NULL) as open_norwoFROM work_order t1,contractor WHEREt1.contractor_id=contractor.contractor_id andcontractor.tms_user_id is not NULL GROUP BYckey,cnam,t1.contractor_id ORDER BY cnam*** Sent via Developersdex http://www.developersdex.com ***Don't just participate in USENET...get rewarded for it!
Hey guys,Here's my situation:I have a table called lets say 'Tree', as illustred bellow:Tree====TreeId (integer)(identity) not nullL1(integer)L2(integer)L3(integer)....L10(integer)The combination of the values of L1 thru L10 is called a "Path" , andL1 thru L10 values are stored in a second table lets say called'Leaf':Leaf====LeafId (integer)(identity) not nullLeatText varchar(2000)Here's my problem:I need to lookup for a given keyword in each path of the tree table,and return each individual column for the paths that match thecriteria. Here's the main idea of how I have this now.SELECT TreeId,L1,L2,...,L10, GetText(L1) + GetText(L2) as L2text + ...+ GetText(L10) AS PathTextINTO #tmp FROM Tree //GetText is a lookup function for the Leaf tableSELECT L1,GetText(L1),L2,GetText(L2),...,L10,GetText(L10) FROM #tmpWHERECharIndex(@keyword,a.pathtext) > 0Does anyone would know a better,smart, more efficient way toaccomplish this task? :)Thks,
I would like to know how can I change a "not in" clause with the same results in a SQL sentence in order to improve the performance of my SQL sentence.
