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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.
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.
Identifier
An identifier specifies the unqualified name of a database object, such as an access method, aggregate, alias, blobspace, cast, column, constraint, correlation, data type, index, operator class, partition, procedure, table, trigger, sequence, synonym, or view. Use the Identifier segment whenever you see a reference to an identifier in a syntax diagram.
Using keywords as table names
The database server issues an error in contexts where the unqualified identifier of a table object is also a valid keyword of SQL. You can disambiguate the table name by qualifying it with the authorization identifier of the owner of the table.
Declaring Keywords or Routine Names as SPL Variables

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.
  - 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.
    - Arguments
    - Collection-Derived Table
      A collection-derived table is a virtual table in which the values in the rows of the table are equivalent to elements of a collection. Use this segment where you see a reference to Collection-Derived Table in a syntax diagram. This syntax is an extension to the ANSI/ISO standard for SQL.
    - Database Name
    - Database Object Name
    - External Routine Reference
      Include the External Routine Reference clause when you write an external routine. This option is not available for SPL routines.
    - Identifier
      An identifier specifies the unqualified name of a database object, such as an access method, aggregate, alias, blobspace, cast, column, constraint, correlation, data type, index, operator class, partition, procedure, table, trigger, sequence, synonym, or view. Use the Identifier segment whenever you see a reference to an identifier in a syntax diagram.
      - Use of Uppercase Characters
      - Use of Keywords as Identifiers
      - Support for Non-ASCII Characters in Identifiers
      - Delimited Identifiers
      - Enabling Delimited Identifiers
      - Potential Ambiguities and Syntax Errors
      - Using the Names of Built-In Functions as Column Names
      - Using Keywords as Column Names
      - Using ALL, DISTINCT, or UNIQUE as a Column Name
      - Using INTERVAL or DATETIME as a Column Name
      - Using rowid as a Column Name
      - Using keywords as table names
        The database server issues an error in contexts where the unqualified identifier of a table object is also a valid keyword of SQL. You can disambiguate the table name by qualifying it with the authorization identifier of the owner of the table.
        Workarounds that Use the Keyword AS
        Using AS with Column Labels
        Using AS with Table Aliases
        Fetching Cursors that have Keywords as Names
        Declaring keywords as names for variables in UDRs
        If you use some keywords as identifiers for variables in a user-defined routine (UDR), you can create ambiguous syntax:
        Using CURRENT, DATETIME, INTERVAL, and NULL in INSERT
        Using NULL and SELECT in a Condition
        Declaring Keywords or Routine Names as SPL Variables
        Variables that Conflict with Column Names
        Using ON, OFF, or PROCEDURE with TRACE
        Using GLOBAL as the Name of a Variable
        Using EXECUTE, SELECT, or WITH as Cursor Names
        SELECT Statements in WHILE and FOR Statements
        SET keyword in the ON EXCEPTION statement of SPL
        If you include an SQL statement that begins with the keyword SET in the ON EXCEPTION statement, you must enclose it in a BEGIN ... END statement block.
    - Jar Name
      Use the Jar Name segment to specify the name of a jar ID. Use this segment whenever you see a reference to Jar Name in a syntax diagram.
    - Optimizer Directives
      The Optimizer Directives segment specifies keywords that you can use to partially or fully specify the query plan of the optimizer. Use this segment whenever you see a reference to Optimizer Directives in a syntax diagram.
    - Owner name
      The owner name specifies the owner of a database object. Use this segment whenever you see a reference to Owner Name in a syntax diagram.
    - Purpose Options
    - Return Clause
    - Routine modifier
      A routine modifier specifies characteristics of how a user-defined routine (UDR) behaves.
    - Routine Parameter List
    - Shared-Object Filename
      Use a shared-object filename to specify a pathname to an executable object file when you register or alter an external routine.
    - Specific Name
    - Statement Block
  - 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.

Declaring Keywords or Routine Names as SPL Variables

If you declare a variable with the same name as a keyword or as the name of a routine, ambiguities can occur. Informix® uses the following rules for resolving name conflicts among SPL variables, UDR names, and built-in SQL function names.

Variable names that are declared in DEFINE statements take the highest precedence.
User-defined routines defined in CREATE PROCEDURE or CREATE FUNCTION statements take precedence over built-in SQL functions.
Procedures declared with the PROCEDURE keyword in the DEFINE statement take precedence over built-in SQL functions.
Built-in SQL functions take precedence over SPL procedures that exist in the database but that are not explicitly identified as procedures in the DEFINE statement.

Do not use the name of a built-in SQL function as an SPL variable if you might need to invoke the SQL function. For example, do not declare a variable with the name count or max, if you might also need to call those aggregate functions.