我有一个错误：
无法创建表“e-learningsystem.chapter”（错误号：121）
在进行工程时，请帮我解决问题
这些是我数据库中的表：
SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0;
SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0;
SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='TRADITIONAL,ALLOW_INVALID_DATES';
CREATE SCHEMA IF NOT EXISTS `E-LearningSystem` DEFAULT CHARACTER SET utf8 COLLATE utf8_general_ci ;
USE `E-LearningSystem` ;
-- -----------------------------------------------------
-- Table `E-LearningSystem`.`Admin`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `E-LearningSystem`.`Admin` (
`AdminID` INT NOT NULL AUTO_INCREMENT ,
`Name` VARCHAR(45) NOT NULL ,
`UserName` VARCHAR(45) NOT NULL ,
`Password` VARCHAR(45) NOT NULL ,
PRIMARY KEY (`AdminID`) )
ENGINE = InnoDB;
-- -----------------------------------------------------
-- Table `E-LearningSystem`.`Semester`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `E-LearningSystem`.`Semester` (
`SemesterID` INT NOT NULL AUTO_INCREMENT ,
`YearID` INT NOT NULL ,
`SemeID` INT NOT NULL ,
PRIMARY KEY (`SemesterID`) )
ENGINE = InnoDB;
-- -----------------------------------------------------
-- Table `E-LearningSystem`.`Lecturer`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `E-LearningSystem`.`Lecturer` (
`LecturerID` INT NOT NULL AUTO_INCREMENT ,
`Name` VARCHAR(45) NOT NULL ,
`Address` VARCHAR(45) NOT NULL ,
`ContactNo` INT NOT NULL ,
`UserName` VARCHAR(45) NOT NULL ,
`Password` VARCHAR(45) NOT NULL ,
`email` VARCHAR(45) NOT NULL ,
PRIMARY KEY (`LecturerID`) )
ENGINE = InnoDB;
-- -----------------------------------------------------
-- Table `E-LearningSystem`.`Subject`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `E-LearningSystem`.`Subject` (
`SubjectID` INT NOT NULL AUTO_INCREMENT ,
`Name` VARCHAR(45) NOT NULL ,
`SemesterID` INT NOT NULL ,
`LecturerID` INT NOT NULL ,
PRIMARY KEY (`SubjectID`) ,
UNIQUE INDEX `SemesterID_UNIQUE` (`SemesterID` ASC) ,
UNIQUE INDEX `LecturerID_UNIQUE` (`LecturerID` ASC) ,
CONSTRAINT `SemesterID`
FOREIGN KEY (`SemesterID` )
REFERENCES `E-LearningSystem`.`Semester` (`SemesterID` )
ON DELETE NO ACTION
ON UPDATE NO ACTION,
CONSTRAINT `LecturerID`
FOREIGN KEY (`LecturerID` )
REFERENCES `E-LearningSystem`.`Lecturer` (`LecturerID` )
ON DELETE NO ACTION
ON UPDATE NO ACTION)
ENGINE = InnoDB;
-- -----------------------------------------------------
-- Table `E-LearningSystem`.`Student`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `E-LearningSystem`.`Student` (
`StudentID` INT NOT NULL AUTO_INCREMENT ,
`Name` VARCHAR(45) NOT NULL ,
`EP_No` VARCHAR(45) NOT NULL ,
`UserName` VARCHAR(45) NOT NULL ,
`Password` VARCHAR(45) NOT NULL ,
`email` VARCHAR(45) NOT NULL ,
PRIMARY KEY (`StudentID`) )
ENGINE = InnoDB;
-- -----------------------------------------------------
-- Table `E-LearningSystem`.`RegisteredStudent`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `E-LearningSystem`.`RegisteredStudent` (
`RegisteredStudentID` INT NOT NULL AUTO_INCREMENT ,
`SubjectID` INT NOT NULL ,
`StudentID` INT NOT NULL ,
`Quiz1` INT NULL ,
`Quiz2` INT NULL ,
`Quiz3` INT NULL ,
`Quiz4` INT NULL ,
`Assignment1` INT NULL ,
`Assignment2` INT NULL ,
`Mid` INT NOT NULL ,
PRIMARY KEY (`RegisteredStudentID`) ,
UNIQUE INDEX `SubjectID_UNIQUE` (`SubjectID` ASC) ,
UNIQUE INDEX `StudentID_UNIQUE` (`StudentID` ASC) ,
CONSTRAINT `SubjectID`
FOREIGN KEY (`SubjectID` )
REFERENCES `E-LearningSystem`.`Subject` (`SubjectID` )
ON DELETE NO ACTION
ON UPDATE NO ACTION,
CONSTRAINT `StudentID`
FOREIGN KEY (`StudentID` )
REFERENCES `E-LearningSystem`.`Student` (`StudentID` )
ON DELETE NO ACTION
ON UPDATE NO ACTION)
ENGINE = InnoDB;
-- -----------------------------------------------------
-- Table `E-LearningSystem`.`Chapter`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `E-LearningSystem`.`Chapter` (
`ChapterID` INT NOT NULL AUTO_INCREMENT ,
`Name` VARCHAR(45) NOT NULL ,
`Document` VARCHAR(45) NOT NULL ,
`SubjectID` INT NOT NULL ,
PRIMARY KEY (`ChapterID`) ,
UNIQUE INDEX `SubjectID_UNIQUE` (`SubjectID` ASC) ,
CONSTRAINT `SubjectID`
FOREIGN KEY (`SubjectID` )
REFERENCES `E-LearningSystem`.`Subject` (`SubjectID` )
ON DELETE NO ACTION
ON UPDATE NO ACTION)
ENGINE = InnoDB;
USE `E-LearningSystem` ;
SET SQL_MODE=@OLD_SQL_MODE;
SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS;
SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS;