composite-primary-key

问题 I have the following three simple classes. How do I go about mapping the Rating class and more specifically its composite key in my Rating.hbm.xml file? I'm currently getting quite lost in the hibernate documentation (5.1.2.1. Composite identifiers) Each rating can have one book and one user making that specific rating. Each user can make many ratings. Each book can have many ratings. Classes Rating class public class Rating { private User user; private Book book; private int rating; private

问题 i have the following scenario (For better illustration, the example is very simplified) Database Model BAS_COSTCODE refers to BAS_CONTEXT. The key for this table is a composite with COSTCODEID and the CONTEXT_FK. CONTEXT_FK refers to BAS_CONTEXT. To build up a hierarchical tree, a CostCode can have a parent. For this reason there is a reference to the table itselfe. The schema file for Context is like that: <?xml version="1.0" encoding="utf-8" ?> <hibernate-mapping xmlns="urn:nhibernate

问题 I'm still a beginner with SQL so please bear with me. I need to create a table that stores information from a form. Each form has an ID associated with it that has two parts. The first part is MMYY and the second part is a 5 digit auto-incrementing integer. An example ID is 0714-00001. And every time the month changes, the 5 digit numbering should start over. So, I want the columns to look something like this: Order_No. | Order_ID ---------------------------- 0714 | 0001 0714 | 0002 0714 |

问题 An app I'm currently designing allows users to create custom competitive leagues (think of it kind of like fantasy sports) and each user can join different leagues and each league consists of multiple rounds where the users (hereafter referred to as Players) will compete and can earn points for different criteria/accomplishments established for each league. Here's some key info to note: Points are accrued across all the rounds during a league/season The custom point criteria/weight settings

问题 I have two tables : report and flyleaf. A report is identified by an 'id' and an 'index' which are foreign and primary keys in flyleaf table. The schema of the tables are : CREATE TABLE `report` ( `id` int(11) NOT NULL, `index` varchar(5) NOT NULL, `nb_page` int(11) DEFAULT NULL ); ALTER TABLE `report` ADD PRIMARY KEY (`id`,`index`); CREATE TABLE `flyleaf_t` ( `id` int(11) NOT NULL, `index` varchar(5) NOT NULL, `title` varchar(30) DEFAULT NULL, `author` varchar(30) DEFAULT NULL, `checker`

问题 I have a table which has a composite primary key made up of one non-auto_increment column and one auto_increment column. The auto_increment column needs to increment individually for each of the non-auto_increment column values (more on this later). The storage engine is InnoDB. I don't wish to lock the table because of performance concerns. After inserting a value, a means to retrieve the last auto_increment value must be available. The below script works at first, but the last INSERT

问题 The EmbeddedId or IdClass annotation is used to denote a composite primary key. How can i use composite primary key without ( EmbeddedId or IdClass ) ? If it is possible to use composite primary key without ( EmbeddedId or IdClass ) then how can i use EntityManager.find( Entity Class , Object primaryKey) method to find entity in case of composite primary key (Multiple Primarykey) (because of no IdClass or EmbeddedId) . EclipseLink take List of pk in the find() operation but if composite pk

问题 I've found a problem with Hibernate and composite key with one of its column auto incremented. I'm using MySQL and primary key composed of 2 columns, GID and LANG. GID column is set as AUTO_INCREMENT. Insert is working, hibernate inserts new row, MySQL adds auto_generated id when GID is null. However, Hibernate doesn't set the GID field in object given to persist. I've heard of problems generally connected with using composite primary key with hibernate, so I'm asking if this is a bug in

问题 I've found a problem with Hibernate and composite key with one of its column auto incremented. I'm using MySQL and primary key composed of 2 columns, GID and LANG. GID column is set as AUTO_INCREMENT. Insert is working, hibernate inserts new row, MySQL adds auto_generated id when GID is null. However, Hibernate doesn't set the GID field in object given to persist. I've heard of problems generally connected with using composite primary key with hibernate, so I'm asking if this is a bug in

问题 In an ERD, a weak/non-identifying relationship is one that connects two strong entities, and is indicated with a dashed line. A strong/identifying relationship is one that connects a strong entity to a weak entity (a weak entity is one that contains the foreign key [FK] from its related entity as a component of its own primary key [PK]), and is indicated by a solid line. My question is, So what? Why is it so important to distinguish between weak/non-identifying relationships versus strong