After planning the database schema, create the database tables for the schema plan. Define the Customers table as follows:

CREATE TABLE Customers (
CustNo NUMBER(3) NOT NULL,
CustName VARCHAR2(30) NOT NULL,
Street VARCHAR2(20) NOT NULL,
City VARCHAR2(20) NOT NULL,
State CHAR(2) NOT NULL,
Zip VARCHAR2(10) NOT NULL,
Phone VARCHAR2(12),
PRIMARY KEY (CustNo)
);

The Customers table stores information about customers. Essential information is defined as NOT NULL. For example, every customer must have a shipping address. However, the Customers table does not manage the relationship between a customer and his or her purchase order. As a result, this relationship must be managed by the Orders table, which you can define as follows:

CREATE TABLE Orders (
PONo NUMBER(5),
Custno NUMBER(3) REFERENCES Customers,
OrderDate DATE,
ShipDate DATE,
ToStreet VARCHAR2(20),
ToCity VARCHAR2(20),
ToState CHAR(2),
ToZip VARCHAR2(10),
PRIMARY KEY (PONo)
);

The line items have a relationship with purchase orders and stock items. The LineItems table manages these relationships using foreign keys. For example, the StockNo foreign key column in the LineItems table references the StockNo primary key column in the StockItems table, which you can define as follows:

CREATE TABLE StockItems (
StockNo NUMBER(4) PRIMARY KEY,
Description VARCHAR2(20),
Price NUMBER(6,2))
);

The Orders table manages the relationship between a customer and purchase order using the CustNo foreign key column, which references the CustNo primary key column in the Customers table. However, the Orders table does not manage the relationship between a purchase order and its line items. As a result, this relationship must be managed by the LineItems table, which you can define as follows:

CREATE TABLE LineItems (
LineNo NUMBER(2),
PONo NUMBER(5) REFERENCES Orders,
StockNo NUMBER(4) REFERENCES StockItems,
Quantity NUMBER(2),
Discount NUMBER(4,2),
PRIMARY KEY (LineNo, PONo)
);