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  • Why connection in Python's DB-API does not have "begin" operation?

    - by newtover
    Working with cursors in mysql-python I used to call "BEGIN;", "COMMIT;", and "ROLLBACK;" explicitly as follows: try: cursor.execute("BEGIN;") # some statements cursor.execute("COMMIT;") except: cursor.execute("ROLLBACK;") then, I found out that the underlying connection object has the corresponding methods: try: cursor.connection.begin() # some statements cursor.connection.commit() except: cursor.connection.rollback() Inspecting the DB-API PEP I found out that it does not mention the begin() method for the connection object, even for the extensions. Mysql-python, by the way, throws the Deprecation Warning, when you use the method. sqlite3.connection, for example, does not have the methd at all. And the question is why there is no such method in the PEP? Is the statement somehow optional, is it enough to invoke commit() instead?

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  • Complex LINQ paging algorithm

    - by sharepointmonkey
    We have a list of projects that may or may not have a collection of subprojects. Our report needs to contain all the projects except those that are the parent project of a subproject. I need to page this into pages of, say, 25 rows. But if subprojects appear on that page then ALL the subprojects of that project must appear on the same page. So more than 25 items may appear if necessary. I've got as far as var pagedProjects = db.Projects.Where(x => !x.SubProjects.Any()).Skip( (pageNo -1) * pageSize).Take(pageSize); Obviously, this fails the second part of the requirements. As a further pain in the arse, I need to have a pager control on the report. So I'll need to be able to calculate the total number of pages. I could loop through the whole table of projects but the performance will suffer. Can anybody come up with a paged solution? EDIT - I should probably mention that SubProjects joins back onto Projects via a selfreferencing foreign key so the whole lot comes back as an IQueryable<Project>.

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  • query optimization

    - by Gaurav
    I have a query of the form SELECT uid1,uid2 FROM friend WHERE uid1 IN (SELECT uid2 FROM friend WHERE uid1='.$user_id.') and uid2 IN (SELECT uid2 FROM friend WHERE uid1='.$user_id.') The problem now is that the nested query SELECT uid2 FROM friend WHERE uid1='.$user_id.' returns a very large number of ids(approx. 5000). The table structure of the friend table is uid1(int), uid2(int). This table is used to determine whether two users are linked together as friends. Any workaround? Can I write the query in a different way? Or is there some other way to solve this issue. I'm sure I am not the first person to face such a problem. Any help would be greatly appreciated.

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  • Subset sum problem

    - by MadBoy
    I'm having a problem with counting which is continuation of this question. I am not really a math person so it's really hard for me to figure out this subset sum problem which was suggested as resolution. I'm having 4 ArrayList in which I hold data: alId, alTransaction, alNumber, alPrice Type | Transaction | Number | Price 8 | Buy | 95.00000000 | 305.00000000 8 | Buy | 126.00000000 | 305.00000000 8 | Buy | 93.00000000 | 306.00000000 8 | Transfer out | 221.00000000 | 305.00000000 8 | Transfer in | 221.00000000 | 305.00000000 8 | Sell | 93.00000000 | 360.00000000 8 | Sell | 95.00000000 | 360.00000000 8 | Sell | 126.00000000 | 360.00000000 8 | Buy | 276.00000000 | 380.00000000 In the end I'm trying to get what's left for customer and what's left I put into 3 array lists: alNew (corresponds to alNumber), alNewPoIle (corresponds to alPrice), and alNewCo (corrseponds to alID) ArrayList alNew = new ArrayList(); ArrayList alNewPoIle = new ArrayList(); ArrayList alNewCo = new ArrayList(); for (int i = 0; i < alTransaction.Count; i++) { string tempAkcjeCzynnosc = (string) alTransaction[i]; string tempAkcjeInId = (string) alID[i]; decimal varAkcjeCena = (decimal) alPrice[i]; decimal varAkcjeIlosc = (decimal) alNumber[i]; int index; switch (tempAkcjeCzynnosc) { case "Transfer out": case "Sell": index = alNew.IndexOf(varAkcjeIlosc); if (index != -1) { alNew.RemoveAt(index); alNewPoIle.RemoveAt(index); alNewCo.RemoveAt(index); } else { ArrayList alTemp = new ArrayList(); decimal varAkcjeSuma = 0; for (int j = 0; j < alNew.Count; j ++) { string akcjeInId = (string) alNewCo[j]; decimal akcjeCena = (decimal) alNewPoIle[j]; decimal akcjeIlosc = (decimal) alNew[j]; if (tempAkcjeInId == akcjeInId && akcjeCena == varAkcjeCena) { alTemp.Add(j); varAkcjeSuma = varAkcjeSuma + akcjeIlosc; } } if (varAkcjeSuma == varAkcjeIlosc) { for (int j = alTemp.Count -1 ; j >=0 ; j --) { int tempIndex = (int) alTemp[j]; alNew.RemoveAt(tempIndex); alNewPoIle.RemoveAt(tempIndex); alNewCo.RemoveAt(tempIndex); } } } break; case "Transfer In": case "Buy": alNew.Add(varAkcjeIlosc); alNewPoIle.Add(varAkcjeCena); alNewCo.Add(tempAkcjeInId); break; } } Basically I'm adding and removing things from Array depending on Transaction Type, Transaction ID and Numbers. I'm adding numbers to ArrayList like 156, 340 (when it is TransferIn or Buy) etc and then i remove them doing it like 156, 340 (when it's TransferOut, Sell). My solution works for that without a problem. The problem I have is that for some old data employees were entering sum's like 1500 instead of 500+400+100+500. How would I change it so that when there's Sell/TransferOut or Buy/Transfer In and there's no match inside ArrayList it should try to add multiple items from thatArrayList and find elements that combine into aggregate. Inside my code I tried to resolve that problem with simple summing everything when there's no match (index == 1) if (index != -1) { alNew.RemoveAt(index); alNewPoIle.RemoveAt(index); alNewCo.RemoveAt(index); } else { ArrayList alTemp = new ArrayList(); decimal varAkcjeSuma = 0; for (int j = 0; j < alNew.Count; j ++) { string akcjeInId = (string) alNewCo[j]; decimal akcjeCena = (decimal) alNewPoIle[j]; decimal akcjeIlosc = (decimal) alNew[j]; if (tempAkcjeInId == akcjeInId && akcjeCena == varAkcjeCena) { alTemp.Add(j); varAkcjeSuma = varAkcjeSuma + akcjeIlosc; } } if (varAkcjeSuma == varAkcjeIlosc) { for (int j = alTemp.Count -1 ; j >=0 ; j --) { int tempIndex = (int) alTemp[j]; alNew.RemoveAt(tempIndex); alNewPoIle.RemoveAt(tempIndex); alNewCo.RemoveAt(tempIndex); } } But it only works if certain conditions are met, and fails for the rest.

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  • How to optimise MySQL query containing a subquery?

    - by aidan
    I have two tables, House and Person. For any row in House, there can be 0, 1 or many corresponding rows in Person. But, of those people, a maximum of one will have a status of "ACTIVE", the others will all have a status of "CANCELLED". e.g. SELECT * FROM House LEFT JOIN Person ON House.ID = Person.HouseID House.ID | Person.ID | Person.Status 1 | 1 | CANCELLED 1 | 2 | CANCELLED 1 | 3 | ACTIVE 2 | 1 | ACTIVE 3 | NULL | NULL 4 | 4 | CANCELLED I want to filter out the cancelled rows, and get something like this: House.ID | Person.ID | Person.Status 1 | 3 | ACTIVE 2 | 1 | ACTIVE 3 | NULL | NULL 4 | NULL | NULL I've achieved this with the following sub select: SELECT * FROM House LEFT JOIN ( SELECT * FROM Person WHERE Person.Status != "CANCELLED" ) Person ON House.ID = Person.HouseID ...which works, but breaks all the indexes. Is there a better solution that doesn't? I'm using MySQL and all relevant columns are indexed. EXPLAIN lists nothing in possible_keys. Thanks.

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  • Jasper error: Caused by SQLServerException: Transaction (Process ID 58) was deadlocked on thread | c

    - by Saky
    I got the above error in my jasper report mail. The query that is used in the report is quite complicated (for me). Reading different posts I conclude that to solve this the I have to change the query to SET TRANSACTION ISOLATION LEVEL REPEATABLE READ GO BEGIN TRANSACTION ... my query ... COMMIT TRANSACTION ? I wonder if this is the correct way to solve the error and that if it has any side effects? Has it happened to anyone in the Jasper reports? Does anyone know if there is a better solution exist to the problem? (Although that I have not yet tested the above solution, if anyone can give any insight on this will be helpful.)

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  • Database table copying

    - by vbNewbie
    I am trying to rectify a previous database creation with tables that contains data that needs to be saved. Instead of recreating a completely new database since some of the tables are still reusable, I need to split a table that exists into 2 new tables which I have done. Now I am trying to insert the data into the 2 new tables and because of duplicate data in the old table I am having a hard time doing this. Old table structure: ClientProjects clientId PK clientName clientProj hashkey MD5 (clientname and clientProj) new table structures: client clientId PK clientName projects queryId PK clientId PK projectName I hope this makes sense. The problem is that in the old table for example you have clients with multiple clientIds.

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  • Swap unique indexed column values in database.

    - by Ramesh Soni
    I have a database table and one of the fields (not primary key) is having unique index on it. Now I want to swap values under this column for two rows. How could this be done? Two hack I know are: Delete both rows and re-insert them Update rows with some other value and swap and then update to actual value. But I don't want to go for these as they do not seem to be the appropriate solution to the problem. Could anyone help me out?

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  • How to reuse results with a schema for end of day stock-data

    - by Vishalrix
    I am creating a database schema to be used for technical analysis like top-volume gainers, top-price gainers etc.I have checked answers to questions here, like the design question. Having taken the hint from boe100 's answer there I have a schema modeled pretty much on it, thusly: Symbol - char 6 //primary Date - date //primary Open - decimal 18, 4 High - decimal 18, 4 Low - decimal 18, 4 Close - decimal 18, 4 Volume - int Right now this table containing End Of Day( EOD) data will be about 3 million rows for 3 years. Later when I get/need more data it could be 20 million rows. The front end will be asking requests like "give me the top price gainers on date X over Y days". That request is one of the simpler ones, and as such is not too costly, time wise, I assume. But a request like " give me top volume gainers for the last 10 days, with the previous 100 days acting as baseline", could prove 10-100 times costlier. The result of such a request would be a float which signifies how many times the volume as grown etc. One option I have is adding a column for each such result. And if the user asks for volume gain in 10 days over 20 days, that would require another table. The total such tables could easily cross 100, specially if I start using other results as tables, like MACD-10, MACD-100. each of which will require its own column. Is this a feasible solution? Another option being that I keep the result in cached html files and present them to the user. I dont have much experience in web-development, so to me it looks messy; but I could be wrong ( ofc!) . Is that a option too? Let me add that I am/will be using mod_perl to present the response to the user. With much of the work on mysql database being done using perl. I would like to have a response time of 1-2 seconds.

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  • Get list of duplicate rows in MySql

    - by user347033
    Hi, i have a table like this ID nachname vorname 1 john doe 2 john doe 3 jim doe 4 Michael Knight I need a query that will return all the fields (select *) from the records that have the same nachname and vorname (in this case, records 1 and 2). Can anyone help me with this? Thanks

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  • Stored Procedure for Multi-Table Insert Error: Cannot Insert the Value Null into Column

    - by SidC
    Good Evening All, I've created the following stored procedure: CREATE PROCEDURE AddQuote -- Add the parameters for the stored procedure here AS BEGIN -- SET NOCOUNT ON added to prevent extra result sets from -- interfering with SELECT statements. SET NOCOUNT ON; Declare @CompanyName nvarchar(50), @Addr nvarchar(50), @City nvarchar(50), @State nvarchar(2), @Zip nvarchar(5), @NeedDate datetime, @PartNumber float, @Qty int -- Insert statements for procedure here Insert into dbo.Customers (CompanyName, Address, City, State, ZipCode) Values (@CompanyName, @Addr, @City, @State, @Zip) Insert into dbo.Orders (NeedbyDate) Values(@NeedDate) Insert into dbo.OrderDetail (fkPartNumber,Qty) Values (@PartNumber,@Qty) END GO When I execute AddQuote, I receive an error stating: Msg 515, Level 16, State 2, Procedure AddQuote, Line 31 Cannot insert the value NULL into column 'ID', table 'Diel_inventory.dbo.OrderDetail'; column does not allow nulls. INSERT fails. The statement has been terminated. I understand that I've set Qty field to not allow nulls and want to continue doing so. However, are there other syntax changes I should make to ensure that this sproc works correctly? Thanks, Sid

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  • TSQL: Global Script Variable?

    - by Abs
    Hello all, I am making use of variables in my TSQL queries. As my script has grown, I have separated each part by GO, now the problem is I need access to variables at the top of my script. How can I still access these variables? Hopefully, this is something simple and straightforward. Thanks all

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  • Best Way to Generate Unique and consecutives numbers in Oracle

    - by RRUZ
    I need to generate unique and consecutive numbers (for use on an invoice), in a fast and reliable way. currently use a Oracle sequence, but in some cases generated numbers are not consecutive because of exceptions that may occur. I thought a couple of solutions to manage this problem, but neither of they convincing me. What solution do you recommend? Use a select max () SELECT MAX (NVL (doc_num, 0)) +1 FROM invoices Use a table to store the last number generated for the invoice. UPDATE docs_numbers SET last_invoice = last_invoice + 1 Another Solution?

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  • Entity Framework doesn't like 0..1 to * relationships.

    - by Orion Adrian
    I have a database framework where I have two tables. The first table has a single column that is an identity and primary key. The second table contains two columns. One is a nvarchar primary key and the other is a nullable foreign key to the first table. On the default import of the database I get the following error: Condition cannot be specified for Column member 'ForeignKeyId' because it is marked with a 'Computed' or 'Identity' StoreGeneratedPattern. where ForeignKeyId is the second foreign key reference in the second table. Is this just something the entity model doesn't do? Or am I missing something?

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  • How do you compare dates in a LINQ query?

    - by Gina
    I am tring to compare a date from a asp calendar control to a date in the table.... here's what i have... it doesn't like the == ? var query = from details in db.TD_TravelCalendar_Details where details.StartDate == calStartDate.SelectedDate && details.EndDate == calEndDate.SelectedDate select details;

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  • Date format error in vb.net ?

    - by ahmed
    I get this error when I run the application Incorrect syntax near 12, on debugging I found that this error is caused due to the # along with the date. Dim backdate as datetime backdate = DateTime.Now.AddDays(-1) on binding the data to the grid to filter the backdate records this error is caused Incorrect syntax near 12. myqry = " select SRNO,SUBJECT,ID where datesend =" backdate Now i am trying to extract only the date or shall I divide the date into day , month and year with DATEPART and take into a variable or convert the date or what should i do , Please help ???

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  • date comparisons in Rails

    - by aressidi
    Hi there, I'm having trouble with a date comparison in a named scope. I'm trying to determine if an event is current based on its start and end date. Here's the named scope I'm using which kind of works, though not for events that have the same start and end date. named_scope :date_current, :conditions => ["Date(start_date) <= ? AND Date(end_date) >= ?", Time.now, Time.now] This returns the following record, though it should return two records, not one... >> Event.date_current => [#<Event id: 2161, start_date: "2010-02-15 00:00:00", end_date: "2010-02-21 00:00:00", ...] What it's not returning is this as well >> Event.find(:last) => #<Event id: 2671, start_date: "2010-02-16 00:00:00", end_date: "2010-02-16 00:00:00", ...> The server time seems to be in UTC and I presume that the entries are being stored in the DB in UTC. Any ideas as to what I'm doing wrong or what to try? Thanks!

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  • LINQ for Java tool

    - by Milhous
    Would a LINQ for java be a useful tool? I have been working on a tool that will allow a Java object to map to a row in a database. Would this be useful for Java programmers? What features would be useful?

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  • How to have multiple tables with multiple joins

    - by williamsdb
    I have three tables that I need to join together and get a combination of results. I have tried using left/right joins but they don't give the desired results. For example: Table 1 - STAFF id name 1 John 2 Fred Table 2 - STAFFMOBILERIGHTS id staffid mobilerightsid rights --this table is empty-- Table 3 - MOBILERIGHTS id rightname 1 Login 2 View and what I need is this as the result... id name id staffid mobilerightsid rights id rightname 1 John null null null null 1 login 1 John null null null null 2 View 2 Fred null null null null 1 login 2 Fred null null null null 2 View I have tried the following : SELECT * FROM STAFFMOBILERIGHTS SMR RIGHT JOIN STAFF STA ON STA.STAFFID = SMR.STAFFID RIGHT JOIN MOBILERIGHTS MRI ON MRI.ID = SMR.MOBILERIGHTSID But this only returns two rows as follows: id name id staffid mobilerightsid rights id rightname null null null null null null 1 login null null null null null null 2 View Can what I am trying to achieve be done and if so how? Thanks

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  • how to update tables' structures keeping current data

    - by Leon
    I have an c# application that uses tables from sqlserver 2008 database (runs on standalone pc with local sqlserver). Initially i install database on this pc with some initial data (there are some tables that application uses and the user doesn't touch). The question is - how can i upgrade this database after user created some new data without harming it (i continue developing and can add some new tables or stored procedures or add some columns to existing tables). Thanks in advance!

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