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  • Help me write a nicer SQL query in Rails

    - by Sainath Mallidi
    Hi, I am trying to write an SQL query to update some of the attributes that are regularly pulled from source. the output will be a text file with the following fields: author, title, date, popularity I have two tables to update one is the author information and the other is popularity table. And the Author Active Record object has one popularity. Currently I'm doing it like this.\ arr.each { |x| x = x.split(" ") results = Author.find_by_sql("SELECT authors.id FROM authors, priorities WHERE authors.id=popularity.authors_id AND authors.author = x[0]") results[0].popularity.update_attribute("popularity", x[3]) I need two tables because the popularity keeps changing, and I need only the top 1000 popular ones, but I still need to keep the previously popular ones also. Is there any nicer way to do this, instead of one query for every new object. Thanks.

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  • merging two tables, while applying aggregates on the duplicates (max,min and sum)

    - by cloudraven
    I have a table (let's call it log) with a few millions of records. Among the fields I have Id, Count, FirstHit, LastHit. Id - The record id Count - number of times this Id has been reported FirstHit - earliest timestamp with which this Id was reported LastHit - latest timestamp with which this Id was reported This table only has one record for any given Id Everyday I get into another table (let's call it feed) with around half a million records with these fields among many others: Id Timestamp - Entry date and time. This table can have many records for the same id What I want to do is to update log in the following way. Count - log count value, plus the count() of records for that id found in feed FirstHit - the earliest of the current value in log or the minimum value in feed for that id LastHit - the latest of the current value in log or the maximum value in feed for that id. It should be noticed that many of the ids in feed are already in log. The simple thing that worked is to create a temporary table and insert into it the union of both as in Select Id, Min(Timestamp) As FirstHit, MAX(Timestamp) as LastHit, Count(*) as Count FROM feed GROUP BY Id UNION ALL Select Id, FirstHit,LastHit,Count FROM log; From that temporary table I do a select that aggregates Min(firsthit), max(lasthit) and sum(Count) Select Id, Min(FirstHit),Max(LastHit),Sum(Count) FROM @temp GROUP BY Id; and that gives me the end result. I could then delete everything from log and replace it with everything with temp, or craft an update for the common records and insert the new ones. However, I think both are highly inefficient. Is there a more efficient way of doing this. Perhaps doing the update in place in the log table?

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  • Hibernate Auto-Increment not working

    - by dharga
    I have a column in my DB that is set with Identity(1,1) and I can't get hibernate annotations to work for it. I get errors when I try to create a new record. In my entity I have the following. @GeneratedValue(strategy=GenerationType.IDENTITY, generator="native") @Column(name="SeqNo", unique=true, nullable=false) BigDecimal seqNo; But when I try to add a new record I get the following error. Cannot insert explicit value for identity column in table 'MemberSelectedOptions' when IDENTITY_INSERT is set to OFF. I don't want to set IDENTIY_INSERT to ON because I want the identity column in the db to manage the values. The SQL that is run is the following; where you can clearly see the insert. insert into dbo.MemberSelectedOptions (OptionStatusCd, EffectiveDate, TermDate, SelectionStatusDate, SysLstUpdtUserId, SysLstTrxDtm, SourceApplication, GroupId, MemberId, OptionId, SeqNo) values (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?) What am I missing?

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  • MySQL query problem

    - by Luke
    Ok, I have the following problem. I have two InnoDB tables: 'places' and 'events'. One place can have many events, but event can be created without entering place. In this case event's foreign key is NULL. Simplified structure of the tables looks as follows: CREATE TABLE IF NOT EXISTS `events` ( `id` int(11) unsigned NOT NULL AUTO_INCREMENT, `name` varchar(255) COLLATE utf8_bin NOT NULL, `places_id` int(9) unsigned DEFAULT NULL, PRIMARY KEY (`id`), KEY `fk_events_places` (`places_id`), ) ENGINE=InnoDB; ALTER TABLE `events` ADD CONSTRAINT `events_ibfk_1` FOREIGN KEY (`places_id`) REFERENCES `places` (`id`) ON DELETE CASCADE ON UPDATE NO ACTION; CREATE TABLE IF NOT EXISTS `places` ( `id` int(9) unsigned NOT NULL AUTO_INCREMENT, `name` varchar(255) COLLATE utf8_bin NOT NULL, PRIMARY KEY (`id`), ) ENGINE=InnoDB; Question is, how to construct query which contains name of the event and name of the corresponding place (or no value, in case there is no place assigned?). I am able to do it with two queries, but then I am visibly separating events which have place assigned from the ones that are without place. Help really appreciated.

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  • Clone current host OS to a guest virtual machine.

    - by ProfKaos
    I would like to run a few repeated checks on a setup procedure I am documenting, to verify my document. I would like to somehow create a VM that replicates the environment on my machine, i.e. the host machine, onto a guest VM. Then I can use Windows' System Restore on the guest to start at the point before I commenced the setup procedure and repeat it as many times as required until no more trial-and-error etc. is required to supplement my document. I have Virtual PC and VirtualBox available to install as host environments, running on Windows 7 Professional.

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  • Virtual directories as DB queries

    I have a site, e.g. site.com I would like users to be able to access it in their locale at site.com/somecity This is similar to craigslist, but they do it with subdomains e.g. sfbay.craigslist.org Using Apache HTTP server. MySql for DB. If you can provide a brief explanation and perhaps links to more thorough discussions, I would be quite interested in learning. I'm developing a web-app and wonder if I should focus some time to read up on Apache, or should I focus more of my time on server-side programming. Thanks!

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  • Strange data swapping error occurs when I attempt to update rows in my table from another table in m

    - by Wesley
    So I have a table of data that is 10,000 lines long. Several of the columns in the table simply describe information about one of the columns, meaning, that only one column has the content, and the rest of the columns describe the location of the content (its for a book). Right now, only 6,000 of the 10,000 rows' content column is filled with its content. Rows 6-10,000's content column simply says null. I have another table in the db that has the content for rows 6,000-10,000, with the correct corresponding primary key which would (seemingly) make it easy to update the 10,000 row table. I have been trying an update query such as the following: UPDATE table(10,000) SET content_column = (SELECT content FROM table(6,000-10,000) WHERE table(10,000).id = table(6-10,000.id) Which kind of works, the only problem is that it pulls in the data from the second table just fine, but it replaces the existing content column with null. So rows 1-6,000's content column become null, and rows 6-10,000's content column have the correct values...Pretty strange I thought anyway. Does anybody have any thoughts about where I am going wrong? If you could show me a better sql query, I would appreciate it! Thanks

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  • Multimap Space Issue: Guava

    - by Arpssss
    In my Java code, I am using Guavas Multimap (com.google.common.collect.Multimap) by using this: Multimap< Integer, Integer Index = HashMultimap.create() Here, Multimap key is some portion of URL and value is another portion of URL (converted into integer). Now, I assign my JVM 2560 Mb (2.5 GB) heap space (by using Xmx and Xms). However, it can only store 9 millions of such (key,value) pairs of integers (approx 10 million). But, theoretically (according to memory occupied by int) it should store more. Can anybody help me, 1) Why is this happening (means Multimap is taking lots of space) ? I checked my code with out inserting pairs in Multimap, it takes only 1/2 MB space. 2) Is there any other way or home-baked solution to solve this space issue ? More clearly, how to solve this memory issue ? Thanks in advance and any idea is perfectly OK for me.

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  • Can't fill a column of NULLs with actual values by making an association to the proper values in the

    - by UkraineTrain
    I have a table with separate columns for months, days and a varchar column for 6 hour increments for each day ('12AM', '6AM', '12PM', '6PM'). There's also a column that's supposed to have calculated numeric values for each of those 6 hour increments. These calculated values come from some reference table. This reference table contains values for each day for several months broken down by hour where each hour has its own column. So, basically, I have to add the values for each 6 hour increment. I have no idea how to associate the correct values in the reference table to those 6 hour increments. I will really appreciate any help on this.

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  • Fastest way to store/retrieve a dictionary - SQL, text file...?

    - by AP257
    Hi all, This is a really really super dumb question, so I apologise, but I'd be grateful for some advice. I've got a text file of words and word frequencies. It's very large - theoretically we're talking millions of rows. I just want to retrieve values from the file, and do it as quickly and efficiently as possible (for a web app, in Django). My question is: what is the best way to store and retrieve the values? Should import them into SQL? Or keep the file and use grep? Or put them into a JSON dictionary...? Or some other way? Sorry for the dumb question, would be very grateful for advice!

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  • Fluent nHibernate - How to map a non-key column on a junction table?

    - by The Matt
    Taking an example that is provided on the Fluent nHibernate website, I need to extend it slightly: I need to add a 'Quantity' column to the StoreProduct table. How would I map this using nHibernate? An example mapping is provided for the given scenario above, but I'm not sure how I would get the Quantity column to map to a property on the Product class: public class StoreMap : ClassMap<Store> { public StoreMap() { Id(x => x.Id); Map(x => x.Name); HasMany(x => x.Employee) .Inverse() .Cascade.All(); HasManyToMany(x => x.Products) .Cascade.All() .Table("StoreProduct"); } }

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  • make db connection persistent throught zend framework

    - by kamikaze_pilot
    I'm using zend framework. currently everytime I need to use the db I go ahead and connect to the DB: function connect(){ $connParams = array("host" => $host, "port" => $port, "username" => $username, "password" => $password, "dbname" => $dbname); $db = new Zend_Db_Adapter_Pdo_Mysql($connParams); return $db } so I would just call the connect() function everytime I need to use the db My question is...suppose I want to reuse $db everywhere in my site and only connect once in the very initial stage of the site load and then close the connection right before the site gets sent to the user, what would be the best practice to accomplish this? Which file in Zend should I save $db in, what method should I use to save it (global variable?), and which file should I do the connection closing in?

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  • How to query range of data in DB2 with highest performance?

    - by Fuangwith S.
    Usually, I need to retrieve data from a table in some range; for example, a separate page for each search result. In MySQL I use LIMIT keyword but in DB2 I don't know. Now I use this query for retrieve range of data. SELECT * FROM( SELECT SMALLINT(RANK() OVER(ORDER BY NAME DESC)) AS RUNNING_NO , DATA_KEY_VALUE , SHOW_PRIORITY FROM EMPLOYEE WHERE NAME LIKE 'DEL%' ORDER BY NAME DESC FETCH FIRST 20 ROWS ONLY ) AS TMP ORDER BY TMP.RUNNING_NO ASC FETCH FIRST 10 ROWS ONLY but I know it's bad style. So, how to query for highest performance?

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  • Using a variable derived from a drop-down list as the column name in a select statement ... Access DB

    - by user1459698
    I'm working with the world's worst DB that was already here so don't blame me for that. So, here's what I have so far ... module = txtModule.value presstype = txtPressType.value SQL_query = "SELECT * FROM tbl_spareparts WHERE '"& module &"' <> '""' AND '"& module &"' = '"& presstype &"' AND Manufacturer = '"& txtsrch.value &"' ORDER BY SAP_Part_No" Set rsData = conn.Execute(SQL_query) This brings up the following SQL statement: SELECT * FROM tbl_spareparts WHERE 'Banyan_Module' <> '"' AND 'Banyan_Module' = 'PB' AND Manufacturer = 'Tester' ORDER BY SAP_Part_No Is there any way I can use the module variable as a column name - obviously the ''s around the column name are causing an error. This is really bothering me. BTW, I'm writing this in VBScript inside a .HTA application page as it has to run locally on tech PCs. Thanks. R.

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  • No operations allowed after statement closed issue

    - by Washu
    I have the next methods in my singleton to execute the JDBC connections public void openDB() throws ClassNotFoundException, IllegalAccessException, InstantiationException, SQLException { Class.forName("com.mysql.jdbc.Driver").newInstance(); String url = "jdbc:mysql://localhost/mbpe_peru";//mydb conn = DriverManager.getConnection(url, "root", "admin"); st = conn.createStatement(); } public void sendQuery(String query) throws SQLException { st.executeUpdate(query); } public void closeDB() throws SQLException { st.close(); conn.close(); } And I'm having a problem in a void where i have to call this twice. private void jButton1ActionPerformed(ActionEvent evt) { Main.getInstance().openDB(); Main.getInstance().sendQuery("call insertEntry('"+EntryID()+"','"+SupplierID()+"');"); Main.getInstance().closeDB(); Main.getInstance().openDB(); for(int i=0;i<dataBox.length;i++){ Main.getInstance().sendQuery("call insertCount('"+EntryID()+"','"+SupplierID()+"','"+BoxID()+"'); Main.getInstance().closeDB(); } } I have already tried to keep the connection open and send the 2 querys and after that closed and it didnt work... The only way it worked was to not use the methods, declare the commands for the connection and use different variables for the connection and the statement. I thought that if i close the Connecion and the Statement I could use the variable once again since is a method but I'm not able to. Is there any way to solve this using my methods for the JDBC connection?

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  • How to find the entity with the greatest primary key?

    - by simpatico
    I've an entity LearningUnit that has an int primary key. Actually, it has nothing more. Entity Concept has the following relationship with it: @ManyToOne @Size(min=1,max=7) private LearningUnit learningUnit; In a constructor of Concept I need to retrieve the LearningUnit with the greatest primary key. If no LearningUnit exists yet I instantiate one. I then set this.learningUnit to the retrieved/instantied. Finally, I call the empty constructor of Concept in a try-catch block, to have the entitymanager do the cardinality check. If an exception is thrown (I expect one in the case that already another 7 Concepts are referring to the same LearningUnit. In that case, I case instantiate a new LearningUnit with a new greater primary key. Please, also point out, if any, clear pitfalls in my outlined algorithm above.

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  • Walking through an SQLite Table

    - by galford13x
    I would like to implement or use functionality that allows stepping through a Table in SQLite. If I have a Table Products that has 100k rows, I would like to retrive perhaps 10k rows at a time. Somthing similar to how a webpage would list data and have a < Previous .. Next > link to walk through the data. Are there select statements that can make this simple? I see and have tried using the ROWID in conjunction with LIMIT which seems ok if not ordering the data. // This seems works if not ordering. SELECT * FROM Products WHERE ROWID BETWEEN x AND y;

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  • Fastest way to do a weighted tag search in SQL Server

    - by Hasan Khan
    My table is as follows ObjectID bigint Tag nvarchar(50) Weight float Type tinyint I want to get search for all objects that has tags 'big' or 'large' I want the objectid in order of sum of weights (so objects having both the tags will be on top) select objectid, row_number() over (order by sum(weight) desc) as rowid from tags where tag in ('big', 'large') and type=0 group by objectid the reason for row_number() is that i want paging over results. The query in its current form is very slow, takes a minute to execute over 16 million tags. What should I do to make it faster? I have a non clustered index (objectid, tag, type) Any suggestions?

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  • Efficient update of SQLite table with many records

    - by blackrim
    I am trying to use sqlite (sqlite3) for a project to store hundreds of thousands of records (would like sqlite so users of the program don't have to run a [my]sql server). I have to update hundreds of thousands of records sometimes to enter left right values (they are hierarchical), but have found the standard update table set left_value = 4, right_value = 5 where id = 12340; to be very slow. I have tried surrounding every thousand or so with begin; .... update... update table set left_value = 4, right_value = 5 where id = 12340; update... .... commit; but again, very slow. Odd, because when I populate it with a few hundred thousand (with inserts), it finishes in seconds. I am currently trying to test the speed in python (the slowness is at the command line and python) before I move it to the C++ implementation, but right now this is way to slow and I need to find a new solution unless I am doing something wrong. Thoughts? (would take open source alternative to SQLite that is portable as well)

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  • how to get transform a local image to a web accessable image

    - by hguser
    Hi: Generally,if we want to display a image in the web page,we give the uri of the image resource like: http://host:port/image/xxx.jpg. Now,there are some images in my file system,and I save its absolute path in the db. Like this; id name address image 1 xxxx xxxx C:/images/xxx.jpg Now if the entity is retrived,its image should be displayed in the page. How to make it? What I thought is copy the image under the web server dir,then build its url,then the page can render it. But I wonder if this is a good idea? Is there any other way?

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  • Synchronizing MySQL databases

    - by Wasim
    Hi all, I have a maintanance problem synchronizing my MySQL data bases . These are the databases I have : My development DB : Here I make my curret development changes . Staging DB : I need to make all the changes I did in the development on it before using , currently I hold migration scripts for structure and data. Production DB : A production environment . Have to do exacly the same as the staging . My problem , is sync. the structure , and some of the data. This is really a very hard work to maintaine. Is there any technics , tools to do with MySQL . What is replication , is it good for my situation , how to use it . Thanks in advance ...

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