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  • Java JPA @OneToMany neededs to reciprocate @ManyToOne?

    - by bguiz
    Create Table A ( ID varchar(8), Primary Key(ID) ); Create Table B ( ID varchar(8), A_ID varchar(8), Primary Key(ID), Foreign Key(A_ID) References A(ID) ); Given that I have created two tables using the SQL statements above, and I want to create Entity classes for them, for the class B, I have these member attributes: @Id @Column(name = "ID", nullable = false, length = 8) private String id; @JoinColumn(name = "A_ID", referencedColumnName = "ID", nullable = false) @ManyToOne(optional = false) private A AId; In class A, do I need to reciprocate the many-to-one relationship? @Id @Column(name = "ID", nullable = false, length = 8) private String id; @OneToMany(cascade = CascadeType.ALL, mappedBy = "AId") private List<B> BList; //<-- Is this attribute necessary? Is it a necessary or a good idea to have a reciprocal @OneToMany for the @ManyToOne? If I make the design decision to leave out the @OneToMany annotated attribute now, will come back to bite me further down.

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  • Grab triangles within a lower triangle

    - by Tyler Rinker
    I have the need to grab all the thee element triangles that make up the lower triangle of a symmetric matrix. I can not think of how to grab all these pieces in the order of far left column working down and then next column to the right and so on. I know that the numbe rof mini triangles inside of the lower triangle is: n = x(x - 1)/2 where: x = nrow(mats[[i]]) Here I've created three matrices with letters (it's easier for me to conceptualize this way) and the elements in the order I'm looking for: FUN <- function(n) { matrix(LETTERS[1:(n*n)], n) } mats <- lapply(3:5, FUN) So this is the output I'd like to get (I put it in code rather than output format) for each of the matrices created above: list(c("B", "C", "F")) list(c("B", "C", "G"), c("C", "D", "H"), c("G", "H", "L")) list(c("B", "C", "H"), c("C", "D", "I"), c("D", "E", "J"), c("H", "I", "N"), c("I", "J", "O"), c("N", "O", "T")) How can I do this task in the fastest manner possible while staying in base R? Not sure if this visual of what I'm after is helpful but it may be:

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  • How to properly reserve identity values for usage in a database?

    - by esac
    We have some code in which we need to maintain our own identity (PK) column in SQL. We have a table in which we bulk insert data, but we add data to related tables before the bulk insert is done, thus we can not use an IDENTITY column and find out the value up front. The current code is selecting the MAX value of the field and incrementing it by 1. Although there is a highly unlikely chance that two instances of our application will be running at the same time, it is still not thread-safe (not to mention that it goes to the database everytime). I am using the ADO.net entity model. How would I go about 'reserving' a range of id's to use, and when that range runs out, grab a new block to use, and guarantee that the same range will not be used.

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  • How to discover table properties from SQLAlchemy mapped object

    - by ssaboum
    Hi, My point is i have a class mapped with a table, in my case in a declarative way, and i want to "discover" table properties, columns, names, relations, from this class : engine = create_engine('sqlite:///' + databasePath, echo=True) # setting up root class for declarative declaration Base = declarative_base(bind=engine) class Ship(Base): __tablename__ = 'ships' id = Column(Integer, primary_key=True) name = Column(String(255)) def __init__(self, name): self.name = name def __repr__(self): return "<Ship('%s')>" % (self.name) So now my goal is from the "Ship" class to get the table columns and their properties from another piece of code. I guess i can deal with it using instrumentation but is there any way provided by the SQLAlchemy API ? Thank you.

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  • Please help, looking for any answer for long time :How to use SqlDataSource Control to work with Dro

    - by Shantanu Gupta
    I am trying to fetch a column value from a datasource when some value is selected from a dropdownlist on its change event. <asp:DropDownList ID="ddlCityName" runat="server" DataSourceID="dsCity" DataTextField="CityName" DataValueField="CityID" AutoPostBack="True" OnTextChanged="CityName_OnTextChanged"> </asp:DropDownList> <asp:SqlDataSource ID="dsCity" runat="server" ConnectionString="<%$ ConnectionStrings:GmapConnectionString %>" SelectCommand="SELECT * FROM [vcity]" ></asp:SqlDataSource> Here I want to fetch any other column's value that is not binded to a ddlCityName from sqldatasource. I have four columns in datasource i.e. name, id, address, phno. I want to fetch an address of a person who selects some value from ddl.

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  • rails migration. modify starting point for auto_increment

    - by railsnew
    I have a table already created. I am looking for a rails migration where I can modify the starting point of the auto_increment number for id column of my table. Let's say I want it to start from 1000. I googled a bit and came across this: it says: :options "string" pass raw options to your underlying database, e.g. auto_increment = 10000. Note that passing options will cause you to lose the default ENGINE=InnoDB statement Can this be used for something I want? and how will the migration look since i am changing the column and not creating new one...

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  • A few problems with Delphi involving Mail Merge, SQL + Databases.

    - by Daniel
    My first problem is with mail merge. I have created a a Data File and a table, yet I am not able to fill my table with information from my Data File. The << just seems to be inserted after wherever the cursor is on the page, which is not where the table is. All that is entered into the actual table is a '59'. Therefore I think I either need to to change the code or be able to move the cursor. Here is the code I am currently using: wrdDoc.Tables.Add(wrdSelection.Range, ADOTable1.FieldCount, 3); wrdDoc.Tables.Item(1).Columns.Item(1).SetWidth(51,wdAdjustNone); wrdDoc.Tables.Item(1).Columns.Item(2).SetWidth(20,wdAdjustNone); wrdDoc.Tables.Item(1).Columns.Item(3).SetWidth(100,wdAdjustNone); // Set the shading on the first row to light gray wrdDoc.Tables.Item(1).Rows.Item(1).Cells .Shading.BackgroundPatternColorIndex := wdGray25; // BOLD the first row wrdDoc.Tables.Item(1).Rows.Item(1).Range.Bold := True; // Center the text in Cell (1,1) wrdDoc.Tables.Item(1).Cell(1,1).Range.Paragraphs.Alignment := wdAlignParagraphCenter; // Fill each row of the table with data wrdDoc.Tables.Item(1).Cell(1, 1).Range.InsertAfter('Time'); wrdDoc.Tables.Item(1).Cell(1, 2).Range.InsertAfter(''); wrdDoc.Tables.Item(1).Cell(1, 3).Range.InsertAfter('Teacher'); For Count := 1 to (ADOTable1.FieldCount - 1) do begin wrdDoc.Tables.Item(1).Cell((Count + 1), 1).Range.InsertAfter(wrdSelection.Range,'Time' + IntToStr(Count)); wrdDoc.Tables.Item(1).Cell((Count + 1), 2).Range.InsertAfter(wrdSelection.Range,'THonorific' + IntToStr(Count)); wrdDoc.Tables.Item(1).Cell((Count + 1), 3).Range.InsertAfter(wrdSelection.Range,'TSurname' + IntToStr(Count)); end; My second problem is that I do not know what the correct SQL syntax is for editing the name of a column in the database (I am using Delphi 7 and Microsoft Jet Engine if that makes a difference). The third problem is that when I add a new column to my database manually (which I need to do) I get a 'violation' error in one of my units when I activate an ADOTable. This only happens on one unit and it happens when I add a column with any name anywhere in the table. I know that is vague but I can't seem to narrow down the problem any further than that. If you could help with me with any of those it would be great. Thanks.

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  • disable a form in asp.net..

    - by rohit
    hi iam working on asp.net using c# project...iam facing a problem...the problem is,i had a master page in which iam using collapse pannel(ajax control)... in collapse pannel i had folders like:- xyz abc def ghi.... and in xyz folder i had some forms.... nw the problem is that i had a search menu in my main page(comes after login)...after searching a grid view is open and in that there is a column name (suppose) XYZ...so when i click on items in that column then only i want xyz folder to be enable or viewed so that i acess forms in that folder....hw cud i do that..i search alot but didn't get the solution..plz help me go through this...

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  • Query a Hibernate many-to-many association

    - by Perry Hoekstra
    In Hibernate HQL, how would you query through a many-to-many association. If I have a Company with multiple ProductLines and other companies can offer these same product lines, I have a Company entity, a ProductLine entity and an association table CompanyProductLine. In SQL, I can get what I need like this: select * from company c where c.companyId in (select companyId from companyProductLine cpl, productline pl where cpl.productLineId = pl.productLineId and pl.name= 'some value'); My problem sees to lie with the association I defined in the Company.hbm.xml file: <set name="productLines" cascade="save-update" table="CompanyProductLine"> <key column="companyId"/> <many-to-many class="com.foo.ProductLine" column="productLineId" /> </set> Any HQL I seem to come up with will throw a: 'expecting 'elements' or 'indices"' Hibernate exception. Thoughts on what the proper HQL would be?

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  • How to get min/max of two integers in Postgres/SQL?

    - by HRJ
    How do I find the maximum (or minimum) of two integers in Postgres/SQL? One of the integers is not a column value. I will give an example scenario: I would like to subtract an integer from a column (in all rows), but the result should not be less than zero. So, to begin with, I have: UPDATE my_table SET my_column = my_column - 10; But this can make some of the values negative. What I would like (in pseudo code) is: UPDATE my_table SET my_column = MAXIMUM(my_column - 10, 0);

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  • Showing renames in hg log?

    - by Ryan Thompson
    I know that Mercurial can track renames of files, but how do I get it to show me renames instead of adds/removes when I do hg log? For instance, instead of: A bin/extract-csv-column.pl A bin/find-mirna-binding.pl A bin/xls2csv-separate-sheets.pl A lib/Text/CSV/Euclid.pm R src/extract-csv-column.pl R src/find-mirna-binding.pl R src/modules/Text/CSV/Euclid.pm R src/xls2csv-separate-sheets.pl I want some indication that four files have been moved. I think I read somewhere that the output is like this to preserve backward-compatibility with something-or-other, but I'm not worried about that.

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  • How to point to other table's ID with hibernate?

    - by Wilhelm
    The problem: let's say I have two tables Client, and Product, in which Client has its primary key and a column called products (that points to pk's in Product table)... ok, if I need products to point only one row, it's nice, but if I need it to point for... 1000 rows in Product table, the products column would have to be larger enought... but I can't predict this situation. So, how could I design my table and how would I use hibernate with it, to achieve that "pointing" in a optmized and maybe "easy" way. NOTE: I excluded some columns of the "design" presented here, just to keep the simplicity.

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  • SQLite subquery syntax/error/difference from MySQL

    - by Rudie
    I was under the impression this is valid SQLite syntax: SELECT *, (SELECT amount AS target FROM target_money WHERE start_year <= p.bill_year AND start_month <= p.bill_month ORDER BY start_year ASC, start_month ASC LIMIT 1) AS target FROM payments AS p; But I guess it's not, because SQLite returns this error: no such column: p.bill_year What's wrong with how I refer to p.bill_year? Yes, I am positive table payments hosts a column bill_year. Am I crazy or is this just valid SQL syntax? It would work in MySQL wouldn't it?? I don't have any other SQL present so I can't test others, but I thought SQLite was quite standardlike.

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  • Get DataGridView checkbox cell value?

    - by George
    Hello guys. I'm having a strange issue here. I have a 3 column datagrid that is filled by a connection with the database. So far so good. I have an extra column, of checkbox type. I need to get it's value for perfoming a bulk operation on it. Here is the catch: When all cells are selected, it works fine. But when an user selects any cell that its not the first, software gives me a object reference exception. Here is the code public List<String> GetSelected() { List<String> selected = new List<String>(); foreach(DataGridViewRow row in datagrid.rows) { if ((Boolean)row.Cells[wantedCell].Value == true) { selected.Add(row.Cells[anotherCell]); } } } I tracked down the failure to the if-test, throwing a exception, because the value of the cell is read as null. Any thougths? Thanks

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  • Fixing "Lock wait timeout exceeded; try restarting transaction" for a 'stuck" Mysql table?

    - by Tom
    From a script I sent a query like this thousands of times to my local database: update some_table set some_column = some_value I forgot to add the where part, so the same column was set to the same a value for all the rows in the table and this was done thousands of times and the column was indexed, so the corresponding index was probably updated too lots of times. I noticed something was wrong, because it took too long, so I killed the script. I even rebooted my computer since them, but something stuck in the table, because simple queries take a very long time to run and when I try dropping the relevant index it fails with this message: Lock wait timeout exceeded; try restarting transaction It's an innodb table, so stuck the transaction is probably implicit. How can I fix this table and remove the stuck transaction from it?

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  • alter mysqldump file before import

    - by julio
    Hi-- I have a mysqldump file created from an earlier version of a product that can't be imported into a new version of the product, since the db structure has changed slightly (mainly altering a column that was NOT NULL DEFAULT 0 to UNIQUE KEY DEFAULT NULL). If I just import the old dump file, it will error out since the column that has default values of 0 now breaks the UNIQUE constraint. It would be easy enough to either manually alter the mysqldump file, or import into a temp table and change it, then copy to the new table. However, is there a way to do this programatically, so it will be repeatable and not manual? (this will need to happen for many instances of this product). I'm thinking something like disabling key constraints for the import, then setting all values that = 0 to NULL, then re-enabling the key constraints? Is this possible? Any help appreciated.

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  • jpa-Primarykey relationship

    - by megala
    Hi created student entity in gogole app engine datastore using JPA. Student---Coding @Entity @Table(name="StudentPersonalDetails", schema="PUBLIC") public class StudentPersonalDetails { @Id @Column(name = "STUDENTNO") private Long stuno; @Basic @Column(name = "STUDENTNAME") private String stuname; public void setStuname(String stuname) { this.stuname = stuname; } public String getStuname() { return stuname; } public void setStuno(Longstuno) { this.stuno = stuno; } public Long getStuno() { return stuno; } public StudentPersonalDetails(Long stuno,String stuname) { this.stuno = stuno; this.stuname = stuname; } } I stored Property value as follows Stuno Stuname 1 a 2 b If i stored Again Stuno No 1 stuname z means it wont allow to insert the record But. It Overwrite the value Stuno Stuname 1 z 2 b How to solve this?

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  • Link a sequence with to an identity in hsqldb

    - by Candy Chiu
    In PostgreSql, one can define a sequence and use it as the primary key of a table. In HsqlDB, one can still accomplish creating an auto-increment identity column which doesn't link to any user defined sequence. Is it possible to use a user defined sequence as the generator of an auto-increment identity column in HsqlDB? Sample sql in PostgreSql: CREATE SEQUENCE seq_company_id START WITH 1; CREATE TABLE company ( id bigint PRIMARY KEY DEFAULT nextval('seq_company_id'), name varchar(128) NOT NULL CHECK (name < '') ); What's the equivalent in HsqlDB? Thanks.

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  • Edit and create nodes in a view?

    - by tputkonen
    We are storing people's class attendance information to Drupal. We would like to show this in a grid/chart, where the first column of each row shows person's name, and rest of the columns (ca. 20) either a checkbox or "X" if the user attended a class, or otherwise an non-checked box or empty column: (dates here) Jack X XXX X X Jill XX XXX XX It should also be possible to edit the attendance information on the grid. Each attendance information is a node of its own. This functionality can probably mostly be achieved using views and editablefields, but there is one problem: if a person has not attended a specific class he/she will not have at all an attendace node for that day. What would be the easiest way to create an attendace node in those cases, so that it would be possible for the end user to edit the grid by just clicking on the checkbox or typing an 'X'?

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  • Advanced queries in HBase

    - by Teflon Ted
    Given the following HBase schema scenario (from the official FAQ)... How would you design an Hbase table for many-to-many association between two entities, for example Student and Course? I would define two tables: Student: student id student data (name, address, ...) courses (use course ids as column qualifiers here) Course: course id course data (name, syllabus, ...) students (use student ids as column qualifiers here) This schema gives you fast access to the queries, show all classes for a student (student table, courses family), or all students for a class (courses table, students family). How would you satisfy the request: "Give me all the students that share at least two courses in common"? Can you build a "query" in HBase that will return that set, or do you have to retrieve all the pertinent data and crunch it yourself in code?

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  • DDEX Firebird editing queries duplicates columns in Visual Studio 2008

    - by A Bothe
    Hello everybody! I don't know if some of you also has experienced it but when I edit a query in Visual Studio (it uses DDEX 2.0.5 for accessing the Firebird 2.5 database), it duplicates some of the columns. What's really interesting is the fact that only System.Boolean columns are duplicated: Originally, there was only ,for instance, a 'PRO_DELETED' field... Now I wanted to sort my results by this field - I had to change the select statement in the so-called QueryBuilder by adding "ORDER BY PRO_DELETED" ...After clicking OK it somehow created a new column (!?) called 'PRO_DELETED1' My question is: Why does DDEX add such a new row to the column view and why can't I access the original PRO_DELETED field anymore? Thanks in advance!

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  • Constant in Hibernate Mapping Files

    - by bertolami
    I would like to add a value object to a mapped class where one column is fixed depending of the class that contains the component. How can I do something like this? <component name="aComponent"> <property name="abc" column="cde"/> <property name="xyz" value="FIXED"/> </component> Unfortunatly, the value attribute does not exist. Is there another way to apply a constant value to property? Thanks in advance.

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  • Oracle TIMESTAMP w/ timezone data type confusion

    - by JuiceBox1337
    When would you use TIMESTAMP w/ timezone as opposed to TIMESTAMP w/ local time zone? When data is stored in a column of data type TIMESTAMP w/ local tz, the data is normalized to the database time zone, and the time zone displacement is not stored as part of the column data. When users retrieve the data, Oracle returns it in the users' local session time zone. Isn't that much more useful? I can't think of a reason why I'd want to use TIMESTAMP w/ timezone and get back some gobble gook with a UTC offset.

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  • How can we block the user from unchecking a DataGridView checkbox?

    - by hawbsl
    We have a DataGridViewCheckBox column bound to a boolean property in our class. The property setter has some logic which says that under certain conditions a True flag cannot be changed, ie, it stays checked forever. This is on a per record basis. So the entire column can't be readonly, only certain rows. Pseudo code: Public Property Foo() As Boolean Get Return _Foo End Get Set(ByVal value As Boolean) If _Foo And Bar And value = False Then //do nothing, in this scenario once you're true, you stay true Else _Foo = value End If End Set End Property Databinding is handling all of this fine, except that the checkbox is visibly cleared when it's clicked. Then, of course, when the binding / setter is fired (as you move off that cell) it is restored to its checked status per the underlying logic. Ultimately it doesn't matter too much but it's a clumsy bit of UI. How can we intercept the user's click and keep it checked?

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  • SQL query - choosing 'last updated' record in a group, better db design?

    - by Jimmy
    Hi, Let's say I have a MySQL database with 3 tables: table 1: Persons, with 1 column ID (int) table 2: Newsletters, with 1 column ID (int) table 3: Subscriptions, with columns Person_ID (int), Newsletter_ID (int), Subscribed (bool), Updated (Datetime) Subscriptions.Person_ID points to a Person, and Subscription.Newsletter_ID points to a Newsletter. Thus, each person may have 0 or more subscriptions to 0 or more magazines at once. The table Subscriptions will also store the entire history of each person's subscriptions to each newsletter. If a particular Person_ID-Newsletter_ID pair doesn't have a row in the Subscriptions table, then it's equivalent to that pair having a subscription status of 'false'. Here is a sample dataset Persons ID 1 2 3 Newsletters ID 4 5 6 Subscriptions Person_ID Newsletter_ID Subscribed Updated 2 4 true 2010-05-01 3 4 true 2010-05-01 3 5 true 2010-05-10 3 4 false 2010-05-15 Thus, as of 2010-05-16, Person 1 has no subscription, Person 2 has a subscription to Newsletter 4, and Person 3 has a subscription to Newsletter 5. Person 3 had a subscription to Newsletter 4 for a while, but not anymore. I'm trying to do 2 kinds of query. A query that shows everyone's active subscriptions as of query time (we can assume that updated will never be in the future -- thus, this means returning the record with the latest 'updated' value for each Person_ID-Newsletter_ID pair, as long as Subscribed is true (if the latest record for a Person_ID-Newsletter_ID pair has a Subscribed status of false, then I don't want that record returned)). A query that returns all active subscriptions for a specific newsletter - same qualification as in 1. regarding records with 'false' in the Subscribed column. I don't use SQL/databases often enough to tell if this design is good, or if the SQL queries needed would be slow on a database with, say, 1M records in the Subscriptions table. I was using the Visual query builder tool in Visual Studio 2010 but I can't even get the query to return the latest updated record for each Person_ID-Newsletter_ID pair. Is it possible to come up with SQL queries that don't involve using subqueries (presumably because they would become too slow with a larger data set)? If not, would it be a better design to have a separate Subscriptions_History table, and every time a subscription status for a Person_ID-Newsletter-ID pair is added to Subscriptions, any existing record for that pair is moved to Subscriptions_History (that way the Subscriptions table only ever contains the latest status update for any Person_ID-Newsletter_ID pair)? I'm using .net on Windows, so would it be easier (or the same, or harder) to do this kind of queries using Linq? Entity Framework? Thanks!

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