MySQL Add foreign KEY statement

SQL statement Format:

· Add FOREIGN KEY constraint: ALTER TABLE from TABLE ADD constraint foreign key (shape: Fk_ from Table _ Main Table) foreign key (from Table foreign key field) references Main Table (primary key field);

Note that the (') in the statement is all the keys under ESC instead of single quotes! The statement is executed as a single quotation mark.

ALTER TABLE T_book add constraint ' FK ' foreign Key (' Booktypeid ') references T_booktype (' id ');
or when creating a table, add it directly

CREATE TABLE T_book (
ID int primary KEY auto_increment,
BookName varchar (20),
Author varchar (10),
Price Decimal (6,2),
Booktypeid int,
Constraint ' FK ' foreign Key (' Booktypeid ') references ' t_booktype ' (' ID ')
);

MySQL Add foreign KEY statement