Code so far

CREATE TABLE PUBLISHER (
        PUBL_CODE    VARCHAR(3),
        NAME             VARCHAR(35) NOT NULL UNIQUE,
        ADDRESS          VARCHAR(80) NOT NULL,
        TELEPHONE        VARCHAR(20) NOT NULL,
        FAX              VARCHAR(20),
        WWW              VARCHAR(40),
        PRIMARY KEY (PUBL_CODE) );

CREATE TABLE SALES_REP (
         REP_ID              VARCHAR(8),
         NAME                VARCHAR(30) NOT NULL,
         PHONE               VARCHAR(20) NOT NULL,
         MOBILE_PHONE        VARCHAR(15),
         EMAIL               VARCHAR(35),
         PUBL_CODE           VARCHAR(3)  NOT NULL,
         PRIMARY KEY (REP_ID),
     FOREIGN KEY (PUBL_CODE) REFERENCES PUBLISHER(PUBL_CODE) );

CREATE TABLE CATEGORY (
        CATEGORY             VARCHAR(4),
        DESCRIPTION          VARCHAR(30) NOT NULL,
     PRIMARY KEY (CATEGORY) );

CREATE TABLE BOOK (
         ISBN                VARCHAR(13),
         TITLE               VARCHAR(150) NOT NULL,
         AUTHOR              VARCHAR(80) NOT NULL,
         YEAR                INT(4),
        BINDING              VARCHAR(14),
        RRP                  DECIMAL(6,2)  NOT NULL,
        QTY_ON_HAND      INT(4),
        MIN_STOCK_LEVEL      INT(2),
     PUBL_CODE           VARCHAR(3) NOT NULL,
        CATEGORY             VARCHAR(4) NOT NULL,
        PRIMARY KEY (ISBN),
     FOREIGN KEY (CATEGORY) REFERENCES CATEGORY(CATEGORY),
     FOREIGN KEY (PUBL_CODE) REFERENCES PUBLISHER(PUBL_CODE) );

CREATE TABLE PURCHASE_INVOICE (
        P_INV_NO         VARCHAR(8),
     P_INV_DATE      DATE  NOT NULL,
         PUBL_CODE       VARCHAR(3)  NOT NULL,
         PRIMARY KEY (P_INV_NO),
     FOREIGN KEY (PUBL_CODE) REFERENCES PUBLISHER(PUBL_CODE) );

CREATE TABLE P_INVOICE_LINE (
         P_INV_NO        VARCHAR(8),
         ISBN                    VARCHAR(13),
         QTY                     INT(4) NOT NULL,
         UNIT_COST           DECIMAL(6,2) NOT NULL,
         PRIMARY KEY (P_INV_NO, ISBN),
     FOREIGN KEY   (P_INV_NO) REFERENCES PURCHASE_INVOICE(P_INV_NO),
     FOREIGN KEY (ISBN) REFERENCES BOOK(ISBN) );