$sql = "CREATE TABLE Teach
(
username varchar(20) not null,
courseName varchar(20) not null,
PRIMARY KEY(username, courseName),
FOREIGN KEY username REFERENCES ON Teacher(username) ON DELETE CASCADE,
FOREIGN KEY courseName REFERENCES ON Course(courseName) ON DELETE CASCADE
);
只要加上那两句外键约束就错了，删掉就对了。
顺便贴上Teacher表的代码吧，Course同理。
$sql = "CREATE TABLE Teacher
(
username varchar(20) not null,
PRIMARY KEY(username)
);
(
username varchar(20) not null,
courseName varchar(20) not null,
PRIMARY KEY(username, courseName),
FOREIGN KEY username REFERENCES ON Teacher(username) ON DELETE CASCADE,
FOREIGN KEY courseName REFERENCES ON Course(courseName) ON DELETE CASCADE
);
只要加上那两句外键约束就错了，删掉就对了。
顺便贴上Teacher表的代码吧，Course同理。
$sql = "CREATE TABLE Teacher
(
username varchar(20) not null,
PRIMARY KEY(username)
);
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