获取错误，当我试图在PostgreSQL中

Question

我想创建使用PostgreSQL

博物馆数据库中创建网桥表我做这一切工作

CREATE DOMAIN lCap as int not null check (VALUE >= 0); 
CREATE TYPE Cap as (min lCap, max lCap); 
CREATE DOMAIN lDim as float8 not null check (VALUE > 0); 
CREATE TYPE lArea as (length lDim, width lDim); 
CREATE DOMAIN lNam as varchar(50) not null; 
CREATE DOMAIN lDoor as smallint not null; 

create table Locations 
(
    locSerial  serial not null primary key, 
    locName   lNam, 
    locDimensions  lArea, 
    locCapacity  Cap, 
    locDoors  lDoor 
); 

CREATE DOMAIN eTime as timestamp not null; 
CREATE DOMAIN eNam as varchar(25) not null; 
CREATE DOMAIN eDescr as varchar(512) not null; 

create table Exhibitions 
(
    exhSerial   serial not null primary key, 
    exhName   eNam, 
    exhDescription  eDescr, 
    exhStrtDate   eTime, 
    exhEndDate  eTime 

); 


CREATE DOMAIN tyID AS smallint not null check (VALUE > 100); 
CREATE DOMAIN tyNam AS varchar(20) not null; 

CREATE TABLE Types(
    typID  tyID primary key, 
    typName  tyNam 

); 


CREATE DOMAIN sID AS smallint not null check (VALUE > 100); 
CREATE DOMAIN sNam AS varchar(30) not null; 

CREATE TABLE Subtypes(
    sbtID  sID PRIMARY KEY, 
    sbtName  sNam 


); 


CREATE DOMAIN mID AS smallint not null check (VALUE > 100); 
CREATE DOMAIN mNam AS varchar(50) not null; 

CREATE TABLE Mediums(
    medID  mID primary key, 
    medName  mNam 

); 


CREATE DOMAIN crID AS smallint not null check (VALUE > 100); 
CREATE DOMAIN crNam AS varchar(35); 

CREATE TABLE Creators(
    creID  crID primary key, 
    creName  crNam 

); 


CREATE DOMAIN wAlphID AS varchar(4) not null; 
CREATE DOMAIN wNumID AS smallint not null check (VALUE > 1000); 
CREATE DOMAIN wObjNam AS varchar(120) not null; 
CREATE DOMAIN wDateMad AS varchar(15) not null; 
CREATE DOMAIN wDateAcqu AS date not null; 
CREATE DOMAIN wInsurValue AS smallint not null; 
CREATE DOMAIN wObjDiscip AS varchar(1000) not null; 

CREATE TABLE Works(
    workAlphID   wAlphID, 
    workNumberID  wNumID, 
    workObjectName  wObjNam, 
    workCreatorNameID  crID, 
    workTypeID   tyID, 
    workSubtypeID  sID, 
    workDateMade  wDateMad, 
    workDateOfAcquisition wDateAcqu, 
    workInsuranceValue  wInsurValue, 
    workObjectDiscription wObjDiscip, 
    primary key (workAlphID,workNumberID), 
    foreign key (workCreatorNameID) references Creators(creID), 
    foreign key (workTypeID) references Types(typID), 
    foreign key (workSubtypeID) references Subtypes(sbtID) 
); 

一切进展顺利达到这个表

但是，当我试图创建此表Works_Mediums作为Works表和媒体表之间的桥梁

我不断收到此错误 错误：没有唯一约束相匹配的引用表中给出钥匙“工程”

CREATE TABLE Works_Mediums(   
    wmedAlphID  wAlphID, 
    wmedNumberID wNumID, 
    wmedID   mID, 
    primary key (wmedAlphID, wmedNumberID, wmedID), 
    foreign key (wmedAlphID) references Works(workAlphID), 
    foreign key (wmedNumberID) references Works(workNumberID), 
    foreign key (wmedID) references Mediums(medID) 
); 

任何想法如何解决这个问题？

方面

Answer 1

这部分

foreign key (wmedAlphID) references Works(workAlphID), 
foreign key (wmedNumberID) references Works(workNumberID), 

应该

foreign key (wmedAlphID, wmedNumberID) references Works (workAlphID, workNumberID), 

PostgreSQL的错误信息都非常优秀。在“Works”表中，唯一约束（在这种情况下是主键约束）位于“workAlphID”和“workNumberID”列的对上。你的外键约束需要引用那对。

唯一约束不一定是主键约束。声明为unique的任何一组列都可以是外键约束的目标。