PSQL错误，没有唯一约束匹配给定表引用的键

Question

I have a baseball database. I'm getting the error Error there is no unique constraint matching given keys for referenced table pitcher.

Here's the schema

CREATE TABLE Teams(
  Name varchar(30) NOT NULL Primary Key,
  Record varchar(10)
);

CREATE TABLE Player(
  Name varchar(30) NOT NULL,
  Num int NOT NULL,
  TeamName varchar(22) references Teams(Name),
  PRIMARY KEY(Name, Num, TeamName),
  Constraint NumCheck Check (Num < 100 and Num > -1)
);

CREATE TABLE Pitcher(
  PHanded varchar(10),
  PName varchar(30),
  PTeamName varchar(30),
  PNum int,
  PRIMARY KEY(PName, PTeamName, PNum),
  foreign key (PName, PTeamName, PNum) references Player(Name, TeamName, Num)
);



CREATE TABLE PosPlayer(
  PPHanded varchar(10),
  Position varchar(2),
  PPName varchar(30),
  PPNum int,
  BTeamName varchar(30),
  PRIMARY KEY(PPName, PPNum, BTeamName),
  foreign key (PPName, PPNum, BTeamName) references Player(Name, Num, TeamName)
);

CREATE TABLE Games(
  Id int Primary Key,
  SchedDate DATE,
  PlayedDate DATE,
  HomeName varchar(30),
  VisitName varchar(30),
  Winner varchar(30)
);


CREATE TABLE Pitches
(
  PID int,
  Outcome varchar(10),
  Bcount int,
  Scount int,
  Runners int,
  Type varchar(10),
  Speed int,
  Pitchnum int,
  PitName varchar(30) references Pitcher(PName),
  PitNum int references Pitcher(PNum),
  PitTeamName varchar(30) references Pitcher(PTeamName),
  BatName varchar(30) references PosPlayer(PPName),
  BatNum int references PosPlayer(PPNum),
  BatTeamName varchar(30) references PosPlayer(BTeamName),
  HomeTName varchar(30),
  VisitTName varchar(30),
  GId int references Games(Id),
  foreign key (PitName, PitNum, PitTeamName) references Pitcher (PName, PNum, PTeamName),
  foreign key (BatName, BatNum, BatTeamName) references PosPlayer (PPName, PPNum, BTeamName),
  Primary Key(PID, PitName, PitNum, PitTeamName, BatName, BatNum, BatTeamName, GID),
  Constraint Balls Check (Bcount > -1 and Bcount < 4),
  Constraint Scount Check (Scount > -1 and Scount < 3)
);

In the other threads I looked up it was suggested to add a unique identifier, but in this schema it is possible to have the same name and be on the same team. How do I fix this?

Answer 1

The lines

CREATE TABLE Pitches
(
{...}
  PitName varchar(30) references Pitcher(PName),
  PitNum int references Pitcher(PNum),
  PitTeamName varchar(30) references Pitcher(PTeamName),
  BatName varchar(30) references PosPlayer(PPName),
  BatNum int references PosPlayer(PPNum),
  BatTeamName varchar(30) references PosPlayer(BTeamName),
{...}
)

are almost certainly the ones causing you grief. You're trying in each case to reference a nonunique column in the referenced table, and that just won't work.

The good news is that you don't need these references clauses, as they're taken care of by the table-level FOREIGN KEY clauses, each of which references a group of columns whose concatenated values are unique, due to being a composite primary key.