The Contacts example

The Contacts database illustrates why and how to partition tables that do not contain the subscription expression.

Example

Here is a simple database that illustrates the problem.

The Contacts table has a foreign key to the Customers table. The Customers table has a foreign key to the SalesReps table.

Each sales representative sells to several customers. At some customers there is a single contact, while other customers have several contacts.

The tables in the database

The three tables are described in more detail as follows:

Table

Description

SalesReps

All sales representatives that work for the company. The SalesReps table has the following columns:

rep_key An identifier for each sales representative. This is the primary key.
name The name of each sales representative.

The SQL statement creating this table is as follows:

CREATE TABLE SalesReps (
   Rep_key CHAR(12) NOT NULL,
   Name CHAR(40) NOT NULL,
   PRIMARY KEY (rep_key)
);

Customers

All customers that do business with the company. The Customers table includes the following columns:

cust_key An identifier for each customer. This is the primary key.
name The name of each customer.
rep_key An identifier for the sales representative in a sales relationship. This is a foreign key to the SalesReps table.

The SQL statement creating this table is as follows:

CREATE TABLE Customers (
   Cust_key CHAR(12) NOT NULL,
   Name CHAR(40) NOT NULL,
   Rep_key CHAR(12) NOT NULL,
   FOREIGN KEY REFERENCES SalesReps,
   PRIMARY KEY (cust_key)
);

Contacts

All individual contacts that do business with the company. Each contact belongs to a single customer. The Contacts table includes the following columns:

contact_key An identifier for each contact. This is the primary key.
name The name of each contact.
cust_key An identifier for the customer to which the contact belongs. This is a foreign key to the Customers table.

The SQL statement creating this table is:

CREATE TABLE Contacts (
   Contacts_key  CHAR(12) NOT NULL,
   Name  CHAR(40) NOT NULL,
   Cust_key  CHAR(12) NOT NULL,
   FOREIGN KEY  REFERENCES Customers,
   PRIMARY KEY  (contact_key)
);

Replication goals

The goals of the design are to provide each sales representative with the following information:

The complete SalesReps table.
Those customers assigned to them, from the Customers table.
Those contacts belonging to the relevant customers, from the Contacts table.

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