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SQL programming
You can use the HCL Informix® implementation of the SQL language to develop applications for Informix database servers.
Guide to SQL: Reference
The Informix® Guide to SQL: Reference contains the reference information for the system catalog tables, data types, and environment variables of the HCL Informix dialect of the SQL language, as implemented in HCL Informix. These topics also include information about the stores_demo, sales_demo, and superstore_demo databases that are included with HCL Informix.
Data types
Every column in a table in a database is assigned a data type. The data type precisely defines the kinds of values that you can store in that column.
Extended Data Types

SQL programming
You can use the HCL Informix® implementation of the SQL language to develop applications for Informix database servers.
- Guide to SQL: Syntax
- Guide to SQL: Reference
  The Informix® Guide to SQL: Reference contains the reference information for the system catalog tables, data types, and environment variables of the HCL Informix dialect of the SQL language, as implemented in HCL Informix. These topics also include information about the stores_demo, sales_demo, and superstore_demo databases that are included with HCL Informix.
  - System catalog tables
    The system catalog consists of tables and views that describe the structure of the database. Sometimes called the data dictionary, these table objects contain everything that the database knows about itself. Each system catalog table contains information about specific elements in the database. Each database has its own system catalog.
  - Data types
    Every column in a table in a database is assigned a data type. The data type precisely defines the kinds of values that you can store in that column.
    - Summary of data types
      HCL Informix® supports the most common set of built-in data types. Additionally, an extended set of data types are supported on the database server.
    - ANSI to Informix data type mapping
    - Description of Data Types
    - Built-In Data Types
    - Extended Data Types
      - Complex data types
        A complex data type can store one or more values of other built-in or extended data types.
      - Distinct Data Types
        A distinct data type has the same internal structure as some other source data type in the database. The source type can be a built-in or extended data type. What distinguishes a distinct type from its source type are support functions that are defined on the distinct type.
      - Opaque Data Types
        An opaque data type is a user-defined or built-in data type that is fully encapsulated. The internal structure of an opaque data type is unknown to the database server.
    - Data Type Casting and Conversion
    - Operator Precedence
  - Environment variables
    Various environment variables affect the functionality of your HCL Informix® products. You can set environment variables that identify your terminal, specify the location of your software and define other parameters.
  - Appendixes
- Guide to SQL: Tutorial
  The Informix® Guide to SQL: Tutorial shows how to use basic and advanced structured query language (SQL) to access and manipulate the data in your databases. It discusses the data manipulation language (DML) statements as well as triggers and stored procedure language (SPL) routines, which DML statements often use.

Extended Data Types

HCL Informix® enables you to create extended data types to characterize data that cannot easily be represented with the built-in data types. (You cannot, however, use extended data types in distributed transactions that query external tables.) You can create these categories of extended data types:

Complex data types
Distinct data types
Opaque data types

Sections that follow provide an overview of each of these data types.

For more information about extended data types, see the Informix® Database Design and Implementation Guide and Informix® User-Defined Routines and Data Types Developer's Guide.