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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.
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).
IF
Conditions in an IF Statement

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).
    - << Label >> statement
      Use the <<label>> statement of SPL to declare a statement label or a loop label.
    - CALL
    - CASE
      Use the CASE statement when program execution needs to take exactly one among multiple branches, depending on the value of an SPL variable or of a simple expression. The CASE statement is a logical alternative to the IF statement.
    - CONTINUE
    - DEFINE
    - EXIT
    - FOR
    - FOREACH
      Use the FOREACH statement to declare a direct cursor that can select and manipulate more than one row from a the result set of a query, or more than one element from a collection.
    - GOTO
    - IF
    - LET
    - LOOP
    - ON EXCEPTION
    - RAISE EXCEPTION
    - RETURN
    - SYSTEM
    - TRACE
    - WHILE
      Use the WHILE statement to establish a loop with variable end conditions.
  - 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.
  - 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.

Conditions in an IF Statement

Just as in the WHILE statement, if any expression in the condition evaluates to NULL, then the condition cannot be true, unless you are explicitly testing for NULL using the IS NULL operator. The following rules summarize NULL values in conditions:

If the expression x evaluates to NULL, then x is not true by definition. Furthermore, NOT (x) is also not true .
IS NULL is the only operator that can return true for x. That is, x IS NULL is true, and x IS NOT NULL is not true.

If an expression in the condition has an UNKNOWN value from an uninitialized SPL variable, the statement terminates and raises an exception.

You can specify a trigger-type Boolean operator (DELETING, INSERTING, SELECTING, or UPDATING) as a condition in an IF statement only within a trigger routine.

IF Statement List

^{(explicit id ifsl002)
ifsl002} ^{(explicit id ifsl003)
ifsl003} ^{(explicit id ifsl004)
ifsl004}

IF Statement List

{ BEGIN <Statement Block>^[] END | <Subset of SPL Statements> ^[] | <Subset of SQL Statements>^[] ; }

¹ See Statement Block

² See Subset of SPL Statements Allowed in the IF Statement List

³ See SQL Statements Not Valid in an IF Statement