CREATE TABLE vendor

( vendor_id int NOT NULL,

vendor_name char(50) NOT NULL,

contact_name char(50),

CONSTRAINT vendors_pk PRIMARY KEY (vendor_id) );

I cant find the foreign key for this table?

CREATE TABLE purchase_order 

( order_number int NOT NULL, 

 order_name char(50) NOT NULL, 

 customer_address char(50), 

 customer_zip int, 

 customer_city char (50), 

 order_total varchar(50), 

CONSTRAINT purchase_order_pk PRIMARY KEY (order_number) ); 

I cant find the foreign key for this table?

create table Inventory(I_Flower_Name varchar(20) ,I_FlowerNumber number , I_Location varchar(20), I_Condition varchar(20), I_Search varchar(40),I_Delete varchar(20), I_Add number,I_Quantity number,PRIMARY KEY (I_Flower_Name,I_FlowerNumber));

I am having trouble adding the foreign key into all three tables?