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Designing databases
The first step in creating a relational database is to construct a data model, which is a precise, complete definition of the data you want to store. After you prepare your data model, you must implement it as a database and tables. To implement your data model, you first select a data type for each column and then you create a database and tables and populate the tables with data. You can also implement fragmentation strategies and control access to your data.
Designing and Implementing a Database
The Informix® Database Design and Implementation Guide provides information to help you design, implement, and manage your Informix databases. It includes data models that illustrate different approaches to database design and shows you how to use structured query language (SQL) to implement and manage your databases.
Object-relational databases
Create and use extended data types in Informix®
Complex data types
Collection data types
MULTISET collection types

Designing databases
The first step in creating a relational database is to construct a data model, which is a precise, complete definition of the data you want to store. After you prepare your data model, you must implement it as a database and tables. To implement your data model, you first select a data type for each column and then you create a database and tables and populate the tables with data. You can also implement fragmentation strategies and control access to your data.
- Designing and Implementing a Database
  The Informix® Database Design and Implementation Guide provides information to help you design, implement, and manage your Informix databases. It includes data models that illustrate different approaches to database design and shows you how to use structured query language (SQL) to implement and manage your databases.

MULTISET collection types

A MULTISET is a collection of elements in which the elements can have duplicate values. For example, a MULTISET of integers might contain the collection {1,3,4,3,3}, which has duplicate elements. You can define a column as a MULTISET collection type when you want to store collections whose elements have the following characteristics:

The elements might not be unique.
The elements have no specific order associated with them.

To illustrate how you might use a MULTISET, suppose that your human resources department wants to keep track of the bonuses awarded to employees in the company. To track each employee's bonuses over time, you can use a MULTISET to define a column in a table that records all the bonuses that each employee receives. In the following example, the bonus column is a MULTISET:

CREATE TABLE employee
(
   name      CHAR(30),
   address   CHAR (40),
   salary    INTEGER,
   bonus     MULTISET(MONEY NOT NULL)
);

You can use the bonus column in this statement to store and access the collection of bonuses for each employee. A query against the bonus column for any given row returns the dollar amount for each bonus that the employee has received. Because an employee might receive multiple bonuses of the same amount (resulting in a collection whose elements are not all unique), the bonus column is defined as a MULTISET, which allows duplicate values.