错误121 mysql有约束

Question

我正在尝试重新定义我的数据库设计添加一些额外的表,所以在我的表Departaments和Jobs中没有重复的名称...

但我得到的错误121与外键有关,你能解释一下这个问题的原因吗？

我在sqlfiddle中这样做

我试图做这样的事情,但在sqlfiddle没有运气,我现在正在工作

 CREATE TABLE Employee(
          EmployeeID  INTEGER      NOT NULL PRIMARY KEY,
          Name        VARCHAR(30)  NOT NULL,
          Sex         CHAR(1)      NOT NULL,
          Address     VARCHAR(80)  NOT NULL,
          Security    VARCHAR(15)  NOT NULL          
        );

        CREATE TABLE Departments  (
            DeptID   INTEGER     NOT NULL PRIMARY KEY,
            DeptName VARCHAR(30) NOT NULL
        );

如果我取消注释代码,我得到 架构创建失败:无法创建表'db_2_2bf4a.project-employee'(错误号:121):

        CREATE TABLE `Dept-Employee`(
          EmployeeID   INTEGER NOT NULL,          
          DeptID       INTEGER NOT NULL,
          CONSTRAINT fk_DeptID     FOREIGN KEY (DeptID)  REFERENCES Departments(DeptID),
          CONSTRAINT fk_EmployeeID FOREIGN KEY (EmployeeID) REFERENCES Employee(EmployeeID)
        );

       CREATE TABLE `Dept-Manager`(
          EmployeeID   INTEGER NOT NULL,          
          DeptID       INTEGER NOT NULL,
          CONSTRAINT fk_DeptID     FOREIGN KEY (DeptID)  REFERENCES Departments(DeptID),
          CONSTRAINT fk_EmployeeID FOREIGN KEY (EmployeeID) REFERENCES Employee(EmployeeID)
        );

        CREATE TABLE Jobs (
            JobID            INTEGER      NOT NULL PRIMARY KEY,
            JobName          VARCHAR(30)  NOT NULL,
            JobSalary        DOUBLE(15,3) NOT NULL default '0.000', 
            JobSalaryperDay  DOUBLE(15,3) NOT NULL default '0.000', 
            DeptID           INTEGER      NOT NULL
        );

        CREATE TABLE `Jobs-Employee`(
          EmployeeID   INTEGER NOT NULL,
          JobID        INTEGER NOT NULL,
          CONSTRAINT fk_JobID      FOREIGN KEY (JobID)      REFERENCES Jobs(JobID),
          CONSTRAINT fk_EmployeeID FOREIGN KEY (EmployeeID) REFERENCES Employee(EmployeeID)
        );

        CREATE TABLE Project(
          ProjectID    INTEGER NOT NULL PRIMARY KEY,
          ProjectDesc   VARCHAR(200) NOT NULL,
          StartDate     DATE NOT NULL,
          EndDate       DATE NOT NULL, 
          DaysOfWork    INTEGER NOT NULL,
          NoEmployees   INTEGER NOT NULL,
          EstimatedCost DOUBLE(15,3) NOT NULL default '0.000', 
          RealCost      DOUBLE(15,3) NOT NULL default '0.000' 
        );


        CREATE TABLE `Project-Employee`(
          ProjectID    INTEGER NOT NULL,
          EmployeeID   INTEGER NOT NULL,
          Note         VARCHAR(200),
          DaysWork     INTEGER NOT NULL,
          CONSTRAINT fk_ProjectID  FOREIGN KEY (ProjectID)  REFERENCES Project(ProjectID),
          CONSTRAINT fk_EmployeeID FOREIGN KEY (EmployeeID) REFERENCES Employee(EmployeeID)
        );

所以在我不知道这个查询是否正确之后

INSERT INTO `Departments` VALUES (1, 'Outsourcing');
    INSERT INTO `Departments` VALUES (2, 'Technician');
    INSERT INTO `Departments` VALUES (3, 'Administrative');

    INSERT INTO `Jobs` VALUES (1, 'welder'    ,500.550,16.7 ,2);
    INSERT INTO `Jobs` VALUES (2, 'turner'    ,500.100,16.67,2);
    INSERT INTO `Jobs` VALUES (3, 'assistant' ,650.100,21.67,2);
    INSERT INTO `Jobs` VALUES (4, 'supervisor',800.909,26.70,3);
    INSERT INTO `Jobs` VALUES (5, 'manager'   ,920.345,30.68,3);
    INSERT INTO `Jobs` VALUES (6, 'counter'   ,520.324,17.35,1);

    INSERT INTO `Dept-Employee` (10,1);
    INSERT INTO `Dept-Employee` (10,2);
    INSERT INTO `Dept-Employee` (10,3);
    INSERT INTO `Dept-Employee` (10,1);
    INSERT INTO `Dept-Employee` (10,3);

    INSERT INTO `Jobs-Employee` (10,3);
    INSERT INTO `Jobs-Employee` (10,3);
    INSERT INTO `Jobs-Employee` (10,4);
    INSERT INTO `Jobs-Employee` (10,6);
    INSERT INTO `Jobs-Employee` (10,5);

    INSERT INTO `Employee` VALUES (10, 'Joe',  'M', 'Anywhere', '927318344');
    INSERT INTO `Employee` VALUES (20, 'Moe',  'M', 'Anywhere', '827318322');
    INSERT INTO `Employee` VALUES (30, 'Jack', 'M', 'Anywhere', '927418343');
    INSERT INTO `Employee` VALUES (40, 'Marge','F', 'Evererre', '127347645');
    INSERT INTO `Employee` VALUES (50, 'Greg' ,'M', 'Portland', '134547633');


    INSERT INTO `Project` VALUES (1, 'The very first', '2008-7-04' , '2008-7-24' , 20, 5, 3000.50, 2500.00);
    INSERT INTO `Project` VALUES (2, 'Second one pro', '2008-8-01' , '2008-8-30' , 30, 5, 6000.40, 6100.40);


    INSERT INTO `Project-Employee` VALUES (1, 10, 'Worked all days'    , 20);
    INSERT INTO `Project-Employee` VALUES (1, 20, 'Worked just in defs', 11);
    INSERT INTO `Project-Employee` VALUES (1, 30, 'Worked just in defs', 17);
    INSERT INTO `Project-Employee` VALUES (1, 40, 'Contability '       , 8);
    INSERT INTO `Project-Employee` VALUES (1, 50, 'Managed the project', 8);

Answer 1

原因是因为CONSTRAINT您提供的名称已存在.尝试更改约束名称.

例如fk_EmployeeID对Dept-Manager 已经存在的Dept-Employee

• SQLFiddle演示