Proper Placement of WHERE Clause in a CREATE CACHE GROUP Statement

In a multiple-table cache group, a WHERE clause in a particular table definition should not reference any table in the cache group other than the table itself. For example, the following CREATE CACHE GROUP statements are valid:

CREATE READONLY CACHE GROUP customer_orders
FROM sales.customer
 (cust_num NUMBER(6) NOT NULL,
  region   VARCHAR2(10),
  name     VARCHAR2(50),
  address  VARCHAR2(100),
  PRIMARY KEY(cust_num))
  WHERE (sales.customer.cust_num < 100),
sales.orders
 (ord_num      NUMBER(10) NOT NULL,
  cust_num     NUMBER(6) NOT NULL,
  when_placed  DATE NOT NULL,
  when_shipped DATE NOT NULL,
  PRIMARY KEY(ord_num),
  FOREIGN KEY(cust_num) REFERENCES sales.customer(cust_num));

CREATE READONLY CACHE GROUP customer_orders
FROM sales.customer
 (cust_num NUMBER(6) NOT NULL,
  region   VARCHAR2(10),
  name     VARCHAR2(50),
  address  VARCHAR2(100),
  PRIMARY KEY(cust_num)),
sales.orders
 (ord_num      NUMBER(10) NOT NULL,
  cust_num     NUMBER(6) NOT NULL,
  when_placed  DATE NOT NULL,
  when_shipped DATE NOT NULL,
  PRIMARY KEY(ord_num),
  FOREIGN KEY(cust_num) REFERENCES sales.customer(cust_num))
  WHERE (sales.orders.cust_num < 100);

The following statement is not valid because the WHERE clause in the child table's definition references its parent table:

CREATE READONLY CACHE GROUP customer_orders
FROM sales.customer
 (cust_num NUMBER(6) NOT NULL,
  region   VARCHAR2(10),
  name     VARCHAR2(50),
  address  VARCHAR2(100),
  PRIMARY KEY(cust_num)),
sales.orders
 (ord_num      NUMBER(10) NOT NULL,
  cust_num     NUMBER(6) NOT NULL,
  when_placed  DATE NOT NULL,
  when_shipped DATE NOT NULL,
  PRIMARY KEY(ord_num),
  FOREIGN KEY(cust_num) REFERENCES sales.customer(cust_num))
  WHERE (sales.customer.cust_num < 100);

Similarly, the following statement is not valid because the WHERE clause in the parent table's definition references its child table:

CREATE READONLY CACHE GROUP customer_orders
FROM sales.customer
 (cust_num NUMBER(6) NOT NULL,
  region   VARCHAR2(10),
  name     VARCHAR2(50),
  address  VARCHAR2(100),
  PRIMARY KEY(cust_num))
  WHERE (sales.orders.cust_num < 100),
sales.orders
 (ord_num      NUMBER(10) NOT NULL,
  cust_num     NUMBER(6) NOT NULL,
  when_placed  DATE NOT NULL,
  when_shipped DATE NOT NULL,
  PRIMARY KEY(ord_num),
  FOREIGN KEY(cust_num) REFERENCES sales.customer(cust_num));