MYSQL外键错误：150无法创建表

我一直在阅读有关StackOverflow和各种论坛关于这个问题，但我似乎无法弄清楚。当试图运行下面的“CREATE TABLE Class”和“CREATE TABLE Enroll”命令时，我得到“ERROR 1005：Can not create table university.class（errno：150）”。我使用InnoDB作为我的存储引擎。前两个“CREATE”语句正常工作。MYSQL外键错误：150无法创建表

我需要做些什么改变才能使“CREATE TABLE Class和CREATE TABLE Enroll”部分起作用？

CREATE TABLE Student (
    stuId VARCHAR(6), 
    lastName VARCHAR(20) NOT NULL, 
    firstName VARCHAR(20) NOT NULL, 
    major VARCHAR(10), 
    credits FLOAT(3) DEFAULT 0, 
    CONSTRAINT Student_stuId_pk PRIMARY KEY (stuId), 
    CONSTRAINT Student_credits_cc CHECK ((credits>=0) AND (credits < 150))); 

CREATE TABLE Faculty (
    facId VARCHAR(6), 
    name VARCHAR(20) NOT NULL, 
    department VARCHAR(20), 
    rank VARCHAR(10), 
    CONSTRAINT Faculty_facId_pk PRIMARY KEY (facId)); 

CREATE TABLE Class (
    classNumber VARCHAR(8), 
    facId VARCHAR(6) NOT NULL, 
    schedule VARCHAR(8), 
    room VARCHAR(6), 
    CONSTRAINT Class_classNumber_pk PRIMARY KEY (classNumber), 
    CONSTRAINT Class_facId_fk FOREIGN KEY (facId) REFERENCES Faculty 
     (facId) ON DELETE SET NULL, 
    CONSTRAINT Class_schedule_room_uk UNIQUE (schedule, room)); 

CREATE TABLE Enroll (
    stuId VARCHAR(6), 
    classNumber VARCHAR(8), 
    grade VARCHAR(2), 
    CONSTRAINT Enroll_classNumber_stuId_pk PRIMARY KEY 
     (classNumber, stuId), 
    CONSTRAINT Enroll_classNumber_fk FOREIGN KEY (classNumber) 
     REFERENCES Class (classNumber) ON DELETE CASCADE, 
CONSTRAINT Enroll_stuId_fk FOREIGN KEY (stuId) REFERENCES Student 
(stuId)ON DELETE CASCADE);

下面是完整的命令和错误：

mysql> CREATE TABLE Class (classNumber VARCHAR(8), facId VARCHAR(6) NOT NULL, schedule VARCHAR(8), room VARCHAR(6), CONSTRAINT Class_classNumber_pk PRIMARY KEY (classNumber), CONSTRAINT Class_facId_fk FOREIGN KEY (facId) REFERENCES Faculty (facId) ON DELETE SET NULL, CONSTRAINT Class_schedule_room_uk UNIQUE (schedule, room)); 
ERROR 1005 (HY000): Can't create table 'university.Class' (errno: 150)

来源

2013-09-26 tbenz9

这可能是因为facId表“类”设置为NOT NULL，但表“教师” facId是不是？ – andrewb

我试着在Faculty表中添加“NOT NULL”，并且在其他两个命令中没有区别。感谢您的想法，但不幸的是它并没有解决我的问题。 – tbenz9

可能的重复：[Mysql创建表与多个外键删除设置null]（http://stackoverflow.com/questions/15880070/mysql-create-table-with-multiple-foreign-key-on-delete-set- null） – aaron