Sql Oracle表中缺少右括号错误

一直扔给我这个：

ORA-00907:缺少右括号

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我做错了什么？

内联外键语法不采用

外键

关键字

考虑：

CREATE TABLE Countries
    (CountryID INT NOT NULL PRIMARY KEY,
    CountryName VARCHAR2(100) NOT NULL,
    RegionID INT FOREIGN KEY REFERENCES Regions(RegionID)
    );

或者，您可以在另一行声明外键，如下所示：

CREATE TABLE Countries (
    CountryID INT NOT NULL PRIMARY KEY,
    CountryName VARCHAR2(100) NOT NULL,
    RegionID INT REFERENCES Regions(RegionID)
);

这同样有效：

CREATE TABLE Countries (
    CountryID INT NOT NULL PRIMARY KEY,
    CountryName VARCHAR2(100) NOT NULL,
    RegionID INT,
    CONSTRAINT fkRegionID FOREIGN KEY (RegionID) REFERENCES Regions(RegionID)
);

CREATE TABLE Countries (
    CountryID INT NOT NULL PRIMARY KEY,
    CountryName VARCHAR2(100) NOT NULL,
    RegionID INT,
    FOREIGN KEY (RegionID) REFERENCES Regions(RegionID)
);