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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.
Basics of database design and implementation
Select data types
Data types
Chronological data types
The chronological data types record time.
Calendar dates: DATE

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.

Calendar dates: DATE

The DATE data type stores a calendar date. A DATE value is actually a signed integer whose contents are interpreted as a count of full days since midnight on December 31, 1899.

The DATE format has ample precision to carry dates into the far future (58,000 centuries). Negative DATE values are interpreted as counts of days before the epoch date; that is, a DATE value of -1 represents December 30, 1899.

Because DATE values are integers, the values can be used in arithmetic expressions. For example, you can take the average of a DATE column, or you can add 7 or 365 to a DATE column. In addition, a rich set of functions exists specifically for manipulating DATE values. For more information, see the Informix® Guide to SQL: Syntax.

The DATE data type is compact, at 4 bytes per item. Arithmetic functions and comparisons execute quickly on a DATE column.