composite-primary-key | 易学教程

How do I create a table with a two primary keys of two foreign keys?

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问题 create table Machine ( Machine_ID int primary key, Machine_Name varchar(30) Machine_Title varchar(30) ) create table Part ( Part_ID int primary key, Part_Name varchar(30), Part_Description varchar(30) ) //How do I make this table below? create table Machine-Part ( Machine_ID int foreign key references (Machine.Machine_ID), Part_ID int foreign key references (Part.Part_ID) Factory_Note varchar(30); ) Mysql complains there is a problem with syntax? Desired Result: have Table 'Machine-Part' use

How do I create a primary key using two foreign keys in Entity Framework 5 code first?

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问题 I have an entity where the primary key consists of two foreign keys to two other tables. I have the configuration working with the following but the table is generated with two FK references. The table: domain.Entity1 MorePK (PK, FK, int, not null) Entity2_Id (PK, FK, int, not null) Entity3_Id (PK, FK, int, not null) OtherData (varchar, null) Entity2_Id1 (FK, int, null) Entity3_Id1 (FK, int, null) is generated from: public Entity1 { public int MorePK { get; set; } public int Entity2_Id { get;

Ruby On Rails multiple composite primary keys question

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I am a new guy in Ruby, and I have tables with these primary keys: transaction_types: transaction_type transaction_headers: transaction_type transaction_year transaction_id transaction_details: transaction_type transaction_year transaction_id city_id ticker_id tickers: city_id ticker_id Of course, those models have other non primary keys such as customer_id, connection_id or date, or user_id, etc, but those are not important for relationships, as those are merely data or I don't have any problem with those. These are my models: #models class transaction_type < ActiveRecord::Base has_many

how to create a composite key in MySQL database

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问题 i am working on mysql server.where i have created a table, named question . column/attributes of this table are (course,subject,year,question) i want to create a primary key(or composite key) consists of (course+subject+year). i.e. for a particular course+subject+year combination there can be only one question.there will be only one row with the combination of (course+subject+year),creation of another row won't be possible. i have done it by : primary key(course,subject,year); but it's not

MongoDB Composite Key: InvalidOperationException: {document}.Identity is not supported

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问题 I am having issues with hydrating a class which consists of a composite ID which in turn has a base class, I am getting an error saying InvalidOperationException: {document}.Identity is not supported. The class i am trying to write to the database is below: public class Product : IEntity<Product> { public readonly Sku Sku; public string Name { get; private set; } public string Description { get; private set; } public bool IsArchived { get; private set; } public Identity<Product> Identity =>

Turnoff mysql unsafe statement warning

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问题 I am using log-error to write warning/errors into a file. When I perform INSERT IGNORE..SELECT statement, it just keep write this warning messages. 120905 3:01:23 [Warning] Unsafe statement written to the binary log using statement format since BINLOG_FORMAT = STATEMENT. INSERT IGNORE... SELECT is unsafe because the order in which rows are retrieved by the SELECT determines which (if any) rows are ignored. This order cannot be predicted and may differ on master and the slave. I want to stop

Only one key from composite primary key as foreign key

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问题 In this database, key1 & key2 make up the composite primary key of table4 , but i'm able to add a foreign key to table3 that comprise just key1 . Why MySQL allows this? Does the above database design make no sense at all? 回答1: TL;DR It's not standard SQL. MySQL documentation itself advises not doing it. In SQL a FOREIGN KEY declaration must reference a column list declared PRIMARY KEY or UNIQUE NOT NULL. (PRIMARY KEY creates a UNIQUE NOT NULL constraint.) (The constraint has to be explicit,

Hibernate find with composite key. Invalid column name Exception

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I'm trying to do a Hibernate Find using a composite Primary key but keep getting the following error: Caused by: org.hibernate.exception.SQLGrammarException: Invalid column name 'merchantNumberAccountTypeId'. at org.hibernate.exception.internal.SQLStateConversionDelegate.convert(SQLStateConversionDelegate.java:122) at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:49) at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:125) at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper

How do I create a table with a two primary keys of two foreign keys?

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create table Machine ( Machine_ID int primary key, Machine_Name varchar(30) Machine_Title varchar(30) ) create table Part ( Part_ID int primary key, Part_Name varchar(30), Part_Description varchar(30) ) //How do I make this table below? create table Machine-Part ( Machine_ID int foreign key references (Machine.Machine_ID), Part_ID int foreign key references (Part.Part_ID) Factory_Note varchar(30); ) Mysql complains there is a problem with syntax? Desired Result: have Table 'Machine-Part' use 'Machine_ID' & 'Part_ID' as both primary keys (which are both foreign keys). If you declare the

JPA OneToOne association where 2 entities use composite primary keys but use different column names?

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We are trying to use Hibernate with a database that uses a lot of composite keys and it's been causing us a lot of headaches. Unfortunately, we can't change the schema so we have to do a lot of additional mapping betwen our fields. We are restricted to using JPA 1.0 and Hibernate 3.3. The biggest problem we've had so far is to do with a one-to-one association between two entities using a composite key of 2 values, where the tables have different names for these columns (the DB has a naming convention of having a table-specific prefix on each column.) Whenever we perform our query, we get this