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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.
Condition

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
      - Comparison Conditions (Boolean Expressions)
        Comparison conditions are often called Boolean expressions because they return a TRUE or FALSE result.
      - Column Name
      - Quotation Marks in Conditions
      - Relational-Operator Condition
        A relational operator compares two expressions quantitatively.
      - BETWEEN Condition
        Use the BETWEEN condition to test whether the value of a numeric, character, or time expression is within a specified range.
      - IN Condition
      - IS NULL and IS NOT NULL Conditions
      - Trigger-Type Boolean Operator
      - LIKE and MATCHES Condition
        A LIKE or MATCHES condition tests for matching character strings.
      - Stand-Alone Condition
      - Condition with Subquery
      - NOT Operator
      - Conditions with AND or OR
        You can combine simple conditions with the logical operators AND or OR to form complex conditions.
    - 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.
    - 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.

Condition

Use a condition to test whether data meets certain qualifications. Use this segment wherever you see a reference to a condition in a syntax diagram.

Syntax

^{(explicit id cond004)
cond004} ^{(explicit id cond005)
cond005} ^{(explicit id cond006)
cond006}

Condition

[ NOT ] { <Comparison Conditions> ^[] | <Condition with Subquery>^[] | <User-Defined Function> ^[] }


Element	Description	Restrictions	Syntax
Logical _Operator	Combines two conditions	Valid options are OR ( = logical union) or AND ( = logical intersection)	Conditions with AND or OR

Usage

A condition is a search criterion, optionally connected by the logical operators AND or OR. Conditions can be classified into the following categories:

Comparison conditions (also called filters or Boolean expressions)
Conditions with a subquery
User-defined functions (Informix® only)

A condition can contain an aggregate function only if it is used in the HAVING clause of a SELECT statement or in the HAVING clause of a subquery.

No aggregate function can appear in a condition in the WHERE clause of a DELETE, SELECT, or UPDATE statement unless both of the following are TRUE:

Aggregate is on a correlated column originating from a parent query.
The WHERE clause appears in a subquery within a HAVING clause.

In Informix®, user-defined functions are not valid as conditions in the following contexts:

In the HAVING clause of a SELECT statement
In the definition of a check constraint

SPL routines are not valid as conditions in the following contexts:

In the definition of a check constraint
In the ON clause of a SELECT statement
In the WHERE clause of a DELETE, SELECT, or UPDATE statement

External routines are not valid as conditions in the following contexts:

In the definition of a check constraint
In the ON clause of a SELECT statement
In the WHERE clause of a DELETE, SELECT, or UPDATE statement
In the WHEN clause of CREATE TRIGGER
In the IF, CASE, or WHILE statements of SPL

¹ See Comparison Conditions (Boolean Expressions)

² See Condition with Subquery

³ See User-Defined Functions