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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
LIKE and MATCHES Condition
A LIKE or MATCHES condition tests for matching character strings.
LIKE Operator
LIKE is the ANSI/ISO standard operator for comparing a column value to another column value, or to a quoted string.

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.
        NOT Operator
        LIKE Operator
        LIKE is the ANSI/ISO standard operator for comparing a column value to another column value, or to a quoted string.
        MATCHES Operator
        The MATCHES operator is the Informix® extension for comparing a column value to another column value, or to a quoted string.
        ESCAPE with LIKE
        The ESCAPE clause can specify an escape character that is different from the default escape character. The default escape character is set by the DEFAULTESCCHAR configuration parameter or the DEFAULTESCCHAR session environment option.
        ESCAPE with MATCHES
        The ESCAPE clause can specify an escape character that is different from the default escape character. The default escape character is set by the DEFAULTESCCHAR configuration parameter or the DEFAULTESCCHAR session environment option.
      - 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.

LIKE Operator

LIKE is the ANSI/ISO standard operator for comparing a column value to another column value, or to a quoted string.

The LIKE operator supports these wildcard characters in the quoted string.

Wildcard: Effect
%: Matches zero or more characters
_: Matches any single character

Besides % and _, LIKE supports a third wildcard character when both the DEFAULTESCCHAR configuration parameter and the DEFAULTESCCHAR session environment variable are not set:

Wildcard: Effect
\: Removes the special significance of the next character (to match a literal % or _ or \ by specifying \% or \_ or \\ )

Using the backslash ( \ ) symbol as the default escape character (when DEFAULTESCCHAR is not set) is the Informix® extension to the ANSI/ISO-standard for SQL. You can specify backslash ( \ ) symbol or some other ASCII character as the default escape character by setting the DEFAULTESCCHAR value to that character. For more information, see DEFAULTESCCHAR session environment option.

In an ANSI-compliant database, you can only use the LIKE escape character to escape a percent sign ( % ), an underscore ( _ ), or the escape character itself.

The following condition tests the description column for the string tennis, alone or in a longer string, such as tennis ball or table tennis paddle:

WHERE description LIKE '%tennis%' ESCAPE '\'

The next example tests description for rows containing an underscore character. Here the backslash ( \ ) escape character is necessary because underscore ( _ ) is a wildcard character.

WHERE description LIKE '%\_%' ESCAPE '\'

The LIKE operator has an associated operator function called like( ). You can define a like( ) function to handle your own user-defined data types. See also Informix® User-Defined Routines and Data Types Developer's Guide.