ERROR 1005（HY000）：无法创建表'... \ issue.frm'（错误号：150）

This is the SQL:

这是SQL:

CREATE TABLE user (
    userID INTEGER UNSIGNED AUTO_INCREMENT PRIMARY KEY NOT NULL,
    username VARCHAR(100) NOT NULL,
    isAdmin BOOL NOT NULL DEFAULT 0,
    canAssignIssue BOOL NOT NULL DEFAULT 0,
    canMarkDuplicate BOOL NOT NULL DEFAULT 0,
    canProcessIssue BOOL NOT NULL DEFAULT 0
) ENGINE = InnoDB;

CREATE TABLE issue (
    issueID INTEGER UNSIGNED AUTO_INCREMENT NOT NULL,
    title VARCHAR(100) NOT NULL,
    body TEXT NOT NULL,
    duplicateOf INTEGER UNSIGNED DEFAULT NULL,
    issueDateTime DATETIME NOT NULL,
    postBy INTEGER UNSIGNED NOT NULL,
    PRIMARY KEY (issueID, postBy, duplicateOf),
    INDEX (postBy, duplicateOf), 
    FOREIGN KEY (duplicateOf) REFERENCES issue (issueID)
        ON DELETE SET NULL,
    FOREIGN KEY (postBy) REFERENCES user (userID)
        ON DELETE SET NULL
) ENGINE = InnoDB;
CREATE TABLE user (