composite-key

i try to create composite primary key in table from 2 foreign key using hibernate JPA,but gives me error.I find some solution on net but nothing The relations between tables looks like this: Table Client clientID(PK) FirstName LastName . Table CarService serviceID(PK) DescriptionOfFailure . . Table ServiceDepartment clientID(PK) serviceID(PK) price . implementation of my code looks like this: @Entity public class ServiceDepartmentBean implements ServiceDepartmentI { @EmbeddedId private ServiceDepartmentPK serviceDepartmentPK = new ServiceDepartmentPK(); @Column(name="clientID", nullable=false,

I have four entities that I would like to translate into database tables via code first fluent api (I'm using a model found at databaseanswers.org), but I'm not certain as to how. The problem I'm having is that SuggestedMenuId is being migrated across two different tables in a Composite key (MenuCourse and CourseRecipeChoice). Here's the message I'm getting: "One or more validation errors were detected during model generation: \tSystem.Data.Entity.Edm.EdmAssociationConstraint: : The number of properties in the Dependent and Principal Roles in a relationship constraint must be identical." Here

I'm trying to create a relation where any of four different parts may be included, but any collection of the same parts should be handled as unique. Example: An assignment must have an assigned company, may optionally have an assigned location, workgroup and program. An assignment may not have a workgroup without a location. Let's assume we have companies A, B, C; locations X, Y, Z; workgroups I, J, K and programs 1, 2, 3. So valid relations could include A - X - I - 1 A - Z - 2 B - Y C C - 3 B - Z - K But invalid relations would include A - K (Workgroup without location) Y - K - 1 (No company

I have a Table with 4 Columns Each Column will be A,B,C,D Column A is the Primary key. Column B has unique name constraint. Now I want to remove the unique constraint for column B and give a unique constraint by combining the columns B, C and D. So the table will allow only one row with a particular value in columns B,C and D. How can I give this type of a constraint? I tried giving the composite unique key like : ALTER TABLE TABLENAME ADD CONSTRAINT CONSTRAINT_NAME UNIQUE (COLUMN_B, COLUMN_C, COLUMN_D) But it is checking whether any one of the constraint is present rather than checking for

Suppose I have a tab delimited file containing user activity data formatted like this: timestamp user_id page_id action_id I want to write a hadoop job to count user actions on each page, so the output file should look like this: user_id page_id number_of_actions I need something like composite key here - it would contain user_id and page_id. Is there any generic way to do this with hadoop? I couldn't find anything helpful. So far I'm emitting key like this in mapper: context.write(new Text(user_id + "\t" + page_id), one); It works, but I feel that it's not the best solution. Just compose your

I have a table with two int values that are IDs. On their own these IDs can show up any number of times in the table, but together they should only ever appear once. Is there a way to make a pair of values unique and still allow the individual values to show up multiple times? As a follow up, if this is possible can the pair of values be used as a key? I currently have a 3rd column for a unique auto increment value for my key. Raphaël Althaus It's called a composite key. If you want to change your actual PK to a composite one, use Alter table <your table> drop PRIMARY KEY; Alter table <your

I'm using Toplink essentials (JPA) + GlassFish v3 + NetBean 6.9 I have one table with composite primary key: table (machine) ---------------- |PK machineId | |PK workId | | | |______________| I created 2 entity classes one for entity itself and second is PK class. public class Machine { @EmbeddedId protected MachinePK machinePK; //getter setters of fields.. } public class MachinePK { @Column(name = "machineId") private String machineId; @Column(name = "workId") private String workId; } Now.. how do I write SELECT clause with JPQL with WHERE??? This fails. SELECT m FROM Machine m WHERE m

create_table :categories_posts, :id => false do |t| t.column :category_id, :integer, :null => false t.column :post_id, :integer, :null => false end I have a join table (as above) with columns that refer to a corresponding categories table and a posts table. I wanted to enforce a unique constraint on the composite key category_id, post_id in the categories_posts join table. But Rails does not support this (I believe). To avoid the potential for duplicate rows in my data having the same combination of category_id and post_id, what's the best workaround for the absence of a composite key in Rails

This is from Hibernate official tutorial : There is an alternative <composite-id> declaration that allows access to legacy data with composite keys. Its use is strongly discouraged for anything else. Why are composite keys discouraged? I am considering using a 3-column table where all of the columns are foreign keys and together form a primary key that is a meaningful relationship in my model. I don't see why this is a bad idea, espicially that I will be using an index on them. What's the alternative? Create an additional automatically generated column and use it as a primary key? I still need