Question

create table Department (
Dep_ID int not null,
Dep_Name varchar(30),
primary key (Dep_ID),
)

create table Course (
C_ID int not null,
C_Name varchar (30) not null,
C_Duration varchar (10) not null,
DegreeType varchar (20),
Dep_ID int,
primary key (C_ID),
constraint DEP_ID1 foreign key (Dep_ID) references Department (Dep_ID) on update cascade,
)


create table Student (
St_ID int not null,
St_Name varchar (100),
St_age smallint,
St_gender Varchar(6),
St_tel int,
St_ADD varchar (100) not null,
St_city varchar (50)not null,
St_type varchar (20) not null,
St_nationality varchar (5) not null,
Dep_ID int,
C_ID int,
primary key (St_ID),
constraint DEP_ID foreign key (Dep_ID) references Department(Dep_ID) on update cascade,
constraint CO_ID foreign key (C_ID) references Course(C_ID) on update cascade,

)

create table Staff (
Sta_ID int not null,
Sta_Name varchar (100) not null,
Sta_type varchar (20) not null,
Sta_Add varchar (100) not null,
Sta_tel int ,
Dep_ID int,
primary key (Sta_ID),
constraint DEeP_ID foreign key (Dep_ID) references Department (Dep_ID) on update cascade,
)

这是我无法使用级联更新的错误复合键

Msg 1785，Level 16，State 0，Line 19 Introducing FOREIGN KEY constraint 'CO_ID' on table 'Student' may cause cycles or multiple cascade paths. Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints。 Msg 1750，Level 16，State 0，Line 19 无法创建约束。查看以前的错误。

Answer 1

您的问题出在表格＆＃39;考试＆＃39;。由于您没有为此表指定任何来源，我只能猜测; - ）

考试包含外键约束Course_ID2

这个外键似乎也适用于部门或课程。

首先看一下这个约束。如果您需要进一步的帮助，请发布表格定义考试，部门和课程的来源

Answer 2

添加外键时

They need to be exactly the same data type in both tables.

尝试使用您的查询它可以正常使用我只需删除＆＃34;，＆＃34;从你的专栏末尾

CREATE TABLE Department (
Dep_ID INT NOT NULL,
Dep_Name VARCHAR(30),
PRIMARY KEY (Dep_ID)
)

CREATE TABLE Course (
C_ID INT NOT NULL,
C_Name VARCHAR (30) NOT NULL,
C_Duration VARCHAR (10) NOT NULL,
DegreeType VARCHAR (20),
Dep_ID INT,
PRIMARY KEY (C_ID),
CONSTRAINT DEP_ID1 FOREIGN KEY (Dep_ID) REFERENCES Department (Dep_ID) ON UPDATE CASCADE
)


CREATE TABLE Student (
St_ID INT NOT NULL,
St_Name VARCHAR (100),
St_age SMALLINT,
St_gender VARCHAR(6),
St_tel INT,
St_ADD VARCHAR (100) NOT NULL,
St_city VARCHAR (50)NOT NULL,
St_type VARCHAR (20) NOT NULL,
St_nationality VARCHAR (5) NOT NULL,
Dep_ID INT,
C_ID INT,
PRIMARY KEY (St_ID),
CONSTRAINT DEP_ID FOREIGN KEY (Dep_ID) REFERENCES Department(Dep_ID) ON UPDATE CASCADE,
CONSTRAINT CO_ID FOREIGN KEY (C_ID) REFERENCES Course(C_ID) ON UPDATE CASCADE

)

CREATE TABLE Staff (
Sta_ID INT NOT NULL,
Sta_Name VARCHAR (100) NOT NULL,
Sta_type VARCHAR (20) NOT NULL,
Sta_Add VARCHAR (100) NOT NULL,
Sta_tel INT ,
Dep_ID INT,
PRIMARY KEY (Sta_ID),
CONSTRAINT DEeP_ID FOREIGN KEY (Dep_ID) REFERENCES Department (Dep_ID) ON UPDATE CASCADE
)

Answer 3

我做了一项研究，并通过更改线路来了解可以解决此问题： constraint CO_ID foreign key (C_ID) references Course(C_ID) on update cascade,至constraint CO_ID foreign key (C_ID) references Course(C_ID) on update No Action,

我在以下链接上获得了解释： Foreign key constraint may cause cycles or multiple cascade paths?

这可能会解决您的问题。

有人可以解释为什么我用sql查询得到这个错误

3 个答案: