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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.
Managing databases
Table fragmentation strategies
Create a fragmented table
Rowids in a fragmented table

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.
  - Basics of database design and implementation
  - Managing databases
    - Table fragmentation strategies
      - What is fragmentation?
      - Distribution schemes for table fragmentation
      - Create a fragmented table
        Create a new fragmented table
        To create a fragmented table, use the FRAGMENT BY clause of the CREATE TABLE statement.
        Create a fragmented table from nonfragmented tables
        Rowids in a fragmented table
        Fragment smart large objects
      - Modify fragmentation strategies
      - Grant and revoke privileges on fragments
    - Grant and limit access to your database
    - Distributed queries
  - Object-relational databases

Rowids in a fragmented table

The term rowid refers to an integer that defines the physical location of a row. The rowid of a row in a nonfragmented table is a unique and constant value. Rows in fragmented tables, in contrast, are not assigned a rowid.

Important: Use primary keys as a method of access in your applications rather than rowids. Because primary keys are defined in the ANSI specification of SQL, using primary keys to access data makes your applications more portable.

To accommodate applications that must reference a rowid for a fragmented table, you can explicitly create a rowid column for a fragmented table. However, you cannot use the WITH ROWIDS clause for typed tables.

To create the rowid column, use the following SQL syntax:

The WITH ROWIDS clause of the CREATE TABLE statement
The ADD ROWIDS clause of the ALTER TABLE statement
The INIT clause of the ALTER FRAGMENT statement

When you create the rowid column, the database server takes the following actions:

Adds the 4-byte unique value to each row in the table
Creates an internal index that it uses to access the data in the table by rowid
Inserts a row in the sysfragments system catalog table for the internal index