composite-primary-key

问题 I have two parent tables: Treatment and Visit . Treatment table: create table Treatment ( TreatCode CHAR(6) constraint cTreatCodeNN not null, Name VARCHAR2(20), constraint cTreatCodePK primary key (TreatCode), ); Visit table: create table Visit ( SlotNum NUMBER(2), DateVisit DATE, ActualArrivalTime DATE, constraint cVisitSlotDatePK primary key (SlotNum, DateVisit) ); Now I try to create a child table: create table Visit_Treat ( TreatCode constraint cTreatCodeFK references Treatment(TreatCode)

问题 How to provide primary key for multiple column in a single table using PostgreSQL? Example: Create table "Test" ( "SlNo" int not null primary key, "EmpID" int not null, /* Want to become primary key */ "Empname" varchar(50) null, "EmpAddress" varchar(50) null ); Note: I want to make "EmpID" also a primary key. 回答1: There can only be one primary key per table. That's what the word "primary" hints at. You can have additional UNIQUE columns. CREATE TABLE test( sl_no int PRIMARY KEY, -- NOT NULL

问题 How to provide primary key for multiple column in a single table using PostgreSQL? Example: Create table "Test" ( "SlNo" int not null primary key, "EmpID" int not null, /* Want to become primary key */ "Empname" varchar(50) null, "EmpAddress" varchar(50) null ); Note: I want to make "EmpID" also a primary key. 回答1: There can only be one primary key per table. That's what the word "primary" hints at. You can have additional UNIQUE columns. CREATE TABLE test( sl_no int PRIMARY KEY, -- NOT NULL

问题 I have 4 tables: User Reports Photos Locations I am allowed to report photos, users, and locations. The primary key of my Reports table is ( User_Id, Reported_Id ) Reported_Id could belong to any of these 3: photos , users and locations . How can I represent this relationship in an entity relationship model? 回答1: The Problem You cannot do this - a foreign key (Reported_Id) cannot reference three tables at once Seems to be a problem regarding the understnading of the data ... rather than a

问题 I have 4 tables: User Reports Photos Locations I am allowed to report photos, users, and locations. The primary key of my Reports table is ( User_Id, Reported_Id ) Reported_Id could belong to any of these 3: photos , users and locations . How can I represent this relationship in an entity relationship model? 回答1: The Problem You cannot do this - a foreign key (Reported_Id) cannot reference three tables at once Seems to be a problem regarding the understnading of the data ... rather than a

问题 We have recently added a new "level" to our database - added a key "Company_ID" to be above/before the existing ID Identity field in the tables throughout the database. For example, if a Table had ID then fields, it now has Company_ID, then ID, then the fields. The idea is that this allows ID to auto-increment for each different Company_ID value that is provided to the functionality (Company_ID 1 can have ID 1, 2, 3 etc ; Company_ID 2 can have ID 1, 2, 3, etc). The auto-increment field

问题 I have this entity class having more than one primary key ( @Id ) which resulted me to use @RooJpaActiveRecord(identifierType = '<IdentifierClass.class>') and @RooIdentifier(dbManaged=true) . Yet I am having a problem on accessing Identifier.class from the entity class itself. My questions is how can I access Identifier in the entity class without, at most, removing the @RooJpaActiveRecord(identifierType = '<Identifier.class>') code. 回答1: Roo will generate a property id on your entity. This

问题 I am trying to map a composite key for an entity. public class Customer { public int CustomerId { get; set; } public virtual List<CustomerImage> CustomerImages { get; set; } } And its Map: public class CustomerMap : EntityTypeConfiguration<Customer> { public CustomerMap() { HasKey(t => t.CustomerId); ToTable(DbConstants.k_CustomersImageTable); } } An Image: public class Image { public int ImageId { get; set; } } And its map: public class ImageMap : EntityTypeConfiguration<Image> { public

问题 Sorry but I don't know how to call in the Title what I need. I want to create an unique key where each two digits of the number identify other table PK. Lets say I have below Pks in this 3 tables: Id Company Id Area Id Role 1 Abc 1 HR 1 Assistant 2 Xyz 2 Financial 2 Manager 3 Qwe 3 Sales 3 VP Now I need to insert values in other table, I know that I may do in 3 columns and create a Composite Key to reach integrity and uniqueness as below: Id_Company Id_Area Id_Role ...Other_Columns..... 1 2 1

问题 I have a model with one_to_many relatioship: class Work < ActiveRecord::Base has_many :work_right_holders accepts_nested_attributes_for :work_right_holders, allow_destroy: true end class WorkRightHolder < ActiveRecord::Base self.primary_keys = :work_id, :right_holder_id, :role belongs_to :work belongs_to :right_holder end When I try to update a work with nested attributes, it create new instances of object in the relationship, instead of updating the existing based on their primary key: work