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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: Syntax
The Informix® Guide to SQL: Syntax describes the syntax of the statements, data types, expressions, operators, and built-in functions of the Informix dialect of the SQL language.
Data types and expressions
These topics describe the data types and expressions that Informix®supports.
Data Type
The Data Type segment specifies the data type of a column, of a component of a collection, of a field within a ROW type, of a routine parameter, or of a value returned by an expression or by a cast function. Use this segment whenever you see a reference to a data type in a syntax diagram.
Built-In Data Types
Character Data Types
Single-byte and multi-byte characters and locales

SQL programming
You can use the HCL Informix® implementation of the SQL language to develop applications for Informix database servers.
- Guide to SQL: Syntax
  The Informix® Guide to SQL: Syntax describes the syntax of the statements, data types, expressions, operators, and built-in functions of the Informix dialect of the SQL language.
  - Overview of SQL syntax
    These topics provide an overview about how to use the SQL statements, SPL statements, and syntax segments.
  - SQL statements
    This chapter describes the syntax and semantics of SQL statements that are recognized by Informix®.
  - SPL statements
    These topics describe Stored Procedure Language (SPL) statements, which you use to write SPL routines. You can store these routines in the database as user-defined routines (UDRs).
  - Data types and expressions
    These topics describe the data types and expressions that Informix®supports.
    - Scope of Segment Descriptions
    - Use of Segment Descriptions
    - Data type and expression segments
      Data type and expression segments can appear in SQL statements.
    - Collection Subquery
    - Condition
    - Data Type
      The Data Type segment specifies the data type of a column, of a component of a collection, of a field within a ROW type, of a routine parameter, or of a value returned by an expression or by a cast function. Use this segment whenever you see a reference to a data type in a syntax diagram.
      - Built-In Data Types
        BOOLEAN and other built-in opaque data types
        Informix® also supports the BOOLEAN data type, which is a built-in opaque data type that can store true, false, or NULL values. The symbol t represents a literal BOOLEAN true value, and f represents a literal BOOLEAN false value.
        BSON and JSON built-in opaque data types
        The BSON and JSON data types are built-in opaque types of Informix® that can be accessed and manipulated in local and distributed queries and in other DML operations. These are SQL data types that directly support relational database operations on data in BSON or JSON document store format. However, if you plan to query JSON and BSON data through the wire listener, you must create your database objects, such as collections and indexes, through the wire listener. You can use SQL statements to query JSON and BSON data whether you created your database objects through the wire listener or with SQL statements.
        Character Data Types
        Single-byte and multi-byte characters and locales
        Fixed- and Varying-Length Character Data Types
        LVARCHAR Data Type
        NCHAR and NVARCHAR data types
        The character data types NCHAR and NVARCHAR can support a localized order of collation in some database locales. In databases created with the NLSCASE INSENSITIVE property, NCHAR and NVARCHAR columns (and string values that are cast to these data types) can support case-insensitive queries.
        IDSSECURITYLABEL Data Type
        In a table that is protected by a label-based security policy, the IDSSECURITYLABEL data type of Informix® stores a security label.
        Numeric Data Types
        Exact Numeric Data Types
        Approximate Numeric Data Types
        Large-Object Data Types
        Time Data Types
        The time data types store calendar dates, points in time, and intervals of time.
      - User-Defined Data Type
      - Complex Data Type
    - DATETIME Field Qualifier
      Use a DATETIME Field Qualifier to specify the largest and smallest unit of time in a DATETIME column or value. Use this segment whenever you see a reference to a DATETIME Field Qualifier in a syntax diagram.
    - Expression
    - OLAP window expressions
      You can include On-Line Analytical Processing (OLAP) expressions in a SELECT statement to operate on subsets of the rows in the result set of a query or subquery. You can use OLAP window expressions to examine subsets of the qualifying rows for patterns, trends, or exceptions in the data.
    - INTERVAL Field Qualifier
    - Literal Collection
    - Literal DATETIME
      The Literal DATETIME segment specifies a DATETIME value
    - Literal INTERVAL
      The Literal INTERVAL segment specifies a literal INTERVAL value. Use this whenever you see a reference to a literal INTERVAL in a syntax diagram.
    - Literal Number
    - Literal Row
      The Literal Row segment specifies the syntax for literal values of named and unnamed ROW data types.
    - Quoted String
    - Relational Operator
  - Other syntax segments
    These topics describe syntax segments, which are language elements, such as database object names or optimizer directives, that appear as a subdiagram reference in the syntax diagrams of some SQL or SPL statements.
  - Built-In Routines
  - Appendixes
- 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.
- 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.

Single-byte and multi-byte characters and locales

All built-in character data types can support single- and multibyte characters in the code set that the DB_LOCALE setting specifies. Locales for most European and Middle Eastern languages support only single-byte code sets, but the UTF-8 code set for the Unicode locale, and code sets for some East Asian locales, such as the Chinese GB18030-2000 locale, support multibyte logical characters.

When the SQL_LOGICAL_CHAR configuration parameter is enabled, you can instruct the database server to interpret explicit or default size parameters in declarations of built-in character data types as specifying the number of logical characters that can be stored, rather than the number of bytes. These logical character semantics are also applied to DISTINCT types whose base types are built-in character types, and to fields of built-in character types in declarations of named or unnamed ROW data types. This feature does not, however, support user-defined data types (UDTs) that store character strings. For more information about this feature, see the Informix® Administrator's Reference description of the SQL_LOGICAL_CHAR configuration parameter.

The TEXT and CLOB data types also support single-byte or multibyte character data, but most built-in functions for manipulating character strings do not support TEXT nor CLOB data. For more information, see Large-Object Data Types.