CREATE TABLE t_teacher(

teacherno INT UNSIGNED PRIMARY KEY,

teachername VARCHAR(20) NOT NULL,

tel CHAR(11) NOT NULL UNIQUE

);

CREATE TABLE t_stu(

id INT UNSIGNED PRIMARY KEY,

login_name VARCHAR(20) NOT NULL,

logpassword VARCHAR(40) NOT NULL,

  telephone CHAR(11) NOT NULL UNIQUE,

teacherno INT UNSIGNED NOT NULL

);

CREATE TABLE t_book(

bookno INT UNSIGNED PRIMARY KEY,

bookname VARCHAR(20) NOT NULL,

writer VARCHAR(20) NOT NULL,

publish_date  DATE NOT NULL,

  publisher VARCHAR(20) NOT NULL,

is_lend char(1),

lenderid int,

borrow_date  DATE,

last_day_return DATE,

return_date DATE

);