can't add foreign key in mysql?
3957 ワード
1 create table department
2 (dept_name varchar(20),
3 building varchar(15),
4 budget numeric(12,2) check (budget > 0),
5 primary key (dept_name)
6 );
7
8 create table course
9 (course_id varchar(8),
10 title varchar(50),
11 dept_name varchar(20),
12 credits numeric(2,0) check (credits > 0),
13 primary key (course_id),
14 foreign key (dept_name) references department
15 on delete set null
16 );
can't add foreign key 。
：MySQL5.6
MySQL5.1 ， 。 ， ： 1 create table department
2 (dept_name varchar(20), 3 building varchar(15), 4 budget numeric(12,2) check (budget > 0), 5 primary key (dept_name) 6 ); 7 8 create table course 9 (course_id varchar(8), 10 title varchar(50), 11 dept_name varchar(20), 12 credits numeric(2,0) check (credits > 0), 13 primary key (course_id), 14 foreign key (dept_name) references department（dept_name） 15 on delete set null 16 );