MySQL错误1215，我做错了什么？

Question

    CREATE TABLE IF NOT EXISTS tblcompany (
    companyid INT(11) UNSIGNED NOT NULL,
    custfirst VARCHAR(50),
    custlast VARCHAR(50),
    company VARCHAR(50),
    custphone VARCHAR(50),
    custemail VARCHAR(50),
    PRIMARY KEY (companyid),
    INDEX (companyid),
    CONSTRAINT FOREIGN KEY (companyid)
        REFERENCES tblproject (companyid)
)  ENGINE=InnoDB;

CREATE TABLE IF NOT EXISTS tblemployee (
    employeeid INT(11) UNSIGNED NOT NULL,
    employeefirst VARCHAR(50),
    employeelast VARCHAR(50),
    employeephone VARCHAR(50),
    employeeemail VARCHAR(50),
    PRIMARY KEY (employeeid),
    INDEX (employeeid),
    CONSTRAINT FOREIGN KEY (employeeid)
        REFERENCES tbltimesheet (employeeid),
    CONSTRAINT FOREIGN KEY (employeeid)
        REFERENCES tblholiday (employeeid),
    CONSTRAINT FOREIGN KEY (employeeid)
        REFERENCES tblannualleave (employeeid)
)  ENGINE=InnoDB;

CREATE TABLE IF NOT EXISTS tblholiday (
    holidayid INT(11) UNSIGNED NOT NULL,
    employeeid INT(11) UNSIGNED NOT NULL,
    holidayfrom DATE,
    holidayto DATE,
    holidayhalfday BOOLEAN,
    holidayreason VARCHAR(50),
    INDEX (employeeid),
    PRIMARY KEY (holidayid)
)  ENGINE=InnoDB;

CREATE TABLE IF NOT EXISTS tblannualleave (
    annualleaveid INT(11) UNSIGNED NOT NULL,
    employeeid INT(11) UNSIGNED NOT NULL,
    annualleavetaken INT(11),
    annualleaveremain INT(11),
    anuualleavetotal INT(11),
    INDEX (employeeid),
    PRIMARY KEY (annualleaveid)
)  ENGINE=InnoDB;

CREATE TABLE IF NOT EXISTS tblproject (
    projectid INT(11) UNSIGNED NOT NULL,
    projectname VARCHAR(50),
    projecttype VARCHAR(50),
    companyid INT(11) UNSIGNED NOT NULL,
    projectnotes VARCHAR(50),
    PRIMARY KEY (projectid),
    INDEX (projectid),
    CONSTRAINT FOREIGN KEY (projectid)
        REFERENCES tbltimesheet (projectid)
)  ENGINE=InnoDB;

CREATE TABLE IF NOT EXISTS tbltimesheet (
    timesheetid INT(11) UNSIGNED NOT NULL,
    employeeid INT(11) UNSIGNED NOT NULL,
    projectid INT(11) UNSIGNED NOT NULL,
    timesheetdate DATE,
    timesheethours INT(11),
    timesheetnotes VARCHAR(50),
    INDEX (employeeid),
    PRIMARY KEY (timesheetid)
)  ENGINE=InnoDB;

11:15:57创建表如果不存在tblcompany（companyid INT（11）无符号NOT NULL,custfirst VARCHAR（50）,custlast VARCHAR（50）,company VARCHAR（50）,custphone VARCHAR（50）,
custemail VARCHAR（50）,主键（companyid）,索引（companyid）,约束外键（companyid）引用tblproject（companyid）Engine=Innodb错误代码：1215。不能添加外键约束0.063秒

谢谢你找我..

Answer 1

在引用表tblproject之前先创建它。

除了错误的表顺序之外，还需要在引用的列上使用主键或唯一键。

SQL小提琴