MySQL不会将外键添加到同一个表中多个外键

Question

我在 Ubuntu 16.04 LTS 上使用 Navicat 时遇到了问题，我正在尝试执行脚本，它在最后一个表上坏了，说无法添加外键约束，这是我的脚本，有人知道我在某处错了吗？

感谢建议

这是我的SQL脚本：

CREATE TABLE `SMER` (
    `Ssmer` INT(10) NOT NULL AUTO_INCREMENT,
    `Nazivs` VARCHAR(255) NOT NULL,
    PRIMARY KEY (`Ssmer`)
    );
CREATE TABLE `Nastavnici` (
    `Snast` INT(10) NOT NULL AUTO_INCREMENT,
    `Imen` VARCHAR(255) NOT NULL,
    PRIMARY KEY (`Snast`)
    );
CREATE TABLE `PREDMETI` (
    `SPRED` INT(10) NOT NULL AUTO_INCREMENT,
    `NAZIVP` VARCHAR(255) NOT NULL,
    PRIMARY KEY (`SPRED`)
    );
CREATE TABLE `Studenti` (
    `Indeks` INT(10) NOT NULL,
    `Upisan` INT(10) NOT NULL,
    `Imes` VARCHAR(255) NOT NULL,
    `Mesto` VARCHAR(255),
    `Datr` DATETIME NOT NULL,
    `Ssmer` INT(10) NOT NULL,
    PRIMARY KEY (`Indeks`, `Upisan`),
    CONSTRAINT `FK_Studenti_Ssmer` FOREIGN KEY (`Ssmer`) REFERENCES `SMER` (`Ssmer`)
    );  
CREATE TABLE `USLOVNI` (
    `Spred` INT(10) NOT NULL,
    `UslPredmet` INT(10) NOT NULL,
    PRIMARY KEY (`Spred`, `UslPredmet`),
    CONSTRAINT `FK_Uslovni_Spred` FOREIGN KEY (`Spred`) REFERENCES `PREDMETI` (`SPRED`),
    CONSTRAINT `FK_Uslovni_UslPredmet` FOREIGN KEY (`UslPredmet`) REFERENCES `PREDMETI` (`SPRED`)
    );
CREATE TABLE `Planst` (
    `Ssmer` INT(10) NOT NULL,
    `Spred` INT(10) NOT NULL,
    `Semestar` VARCHAR(255) DEFAULT NULL,
    PRIMARY KEY (`Ssmer`, `Spred`),
    CONSTRAINT `FK_Planst_Ssmer` FOREIGN KEY (`Ssmer`) REFERENCES `SMER` (`Ssmer`),
    CONSTRAINT `FK_Planst_Spred` FOREIGN KEY (`Spred`) REFERENCES `PREDMETI` (`SPRED`)
    );
CREATE TABLE `Angazovanje` (
    `Snast` INT(10) NOT NULL,
    `Spred` INT(10) NOT NULL,
    `Ssmer` INT(10) NOT NULL,
    PRIMARY KEY (`Snast`, `Spred`, `Ssmer`),
    CONSTRAINT `FK_Angazovanje_Snast` FOREIGN KEY (`Snast`) REFERENCES `Nastavnici` (`Snast`),
    CONSTRAINT `FK_Angazovanje_Spred` FOREIGN KEY (`Spred`) REFERENCES `PREDMETI` (`SPRED`),
    CONSTRAINT `FK_Angazovanje_Ssmer` FOREIGN KEY (`Ssmer`) REFERENCES `SMER` (`Ssmer`)
    );
CREATE TABLE `Prijave` (
    `Spred` INT(10) NOT NULL,
    `Indeks` INT(10) NOT NULL,
    `Upisan` INT(10) NOT NULL,
    `Snast` INT(10) NOT NULL,
    `Datump` DATETIME DEFAULT NOW(),
    `Ocena` INT(2) NOT NULL,
    PRIMARY KEY (`Spred`, `Indeks`, `Upisan`, `Datump`),
    CONSTRAINT `FK_Prijave_Spred` FOREIGN KEY (`Spred`) REFERENCES `PREDMETI` (`SPRED`),
    CONSTRAINT `FK_Prijave_Indeks` FOREIGN KEY (`Indeks`) REFERENCES `Studenti` (`Indeks`),
    CONSTRAINT `FK_Prijave_Upisan` FOREIGN KEY (`Upisan`) REFERENCES `Studenti` (`Upisan`),
    CONSTRAINT `FK_Prijave_Snast` FOREIGN KEY (`Snast`) REFERENCES `Nastavnici` (`Snast`)
    );

以下是错误消息：

     [Err] 1215 - Cannot add foreign key constraint

Answer 1

Prijave表中有两个 FK 指向Studenti表。MySQL在这方面玩得并不好。

试试这个

CONSTRAINT `FK_Prijave_Indeks` FOREIGN KEY (`Indeks`, `Upisan`)
                               REFERENCES `Studenti` (`Indeks`, `Upisan`),

取而代之。

CONSTRAINT `FK_Prijave_Indeks` FOREIGN KEY (`Indeks`) REFERENCES `Studenti` (`Indeks`), /* wrong !*/
CONSTRAINT `FK_Prijave_Upisan` FOREIGN KEY (`Upisan`) REFERENCES `Studenti` (`Upisan`),