CREATE TABLE People (
    PersonId INT PRIMARY KEY AUTO_INCREMENT,
    Name VARCHAR(100) NOT NULL,
    Age INT
);

CREATE TABLE Friendships (
    PersonId INT NOT NULL,
    FriendId INT NOT NULL,
    PRIMARY KEY (PersonId, FriendId),
    FOREIGN KEY (PersonId) REFERENCES People(PersonId) ON DELETE CASCADE,
    FOREIGN KEY (FriendId) REFERENCES People(PersonId) ON DELETE CASCADE,
    CONSTRAINT CHK_NotSelfFriendship CHECK (PersonId != FriendId)
);

CREATE TABLE People (
    PersonId INT PRIMARY KEY AUTO_INCREMENT,
    Name VARCHAR(100) NOT NULL,
    Age INT
);

CREATE TABLE Friendships (
    PersonId INT NOT NULL,
    FriendId INT NOT NULL,
    PRIMARY KEY (PersonId, FriendId),
    FOREIGN KEY (PersonId) REFERENCES People(PersonId) ON DELETE CASCADE,
    FOREIGN KEY (FriendId) REFERENCES People(PersonId) ON DELETE CASCADE,
    CONSTRAINT CHK_NotSelfFriendship CHECK (PersonId != FriendId)
);