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Extending Informix®Beyond standard relational database objects, HCL Informix® can be extended to handle specialized data types, access methods, routines, and other objects. Informix® includes many built-in extensions that are fully integrated in the database server. Informix® also provides DataBlade® modules, which are packages of extended database objects for a particular purpose and that are installed separately from the database server. Alternatively, you can create your own user-defined objects for Informix®.
Creating extensionsYou can create user-defined data types, routines, access methods, and other database objects to suit your needs. You can use application programming interfaces to write user-defined routines and applications that access data in Informix® databases.
DataBlade® API Programmer's GuideThe Informix® DataBlade® API Programmer's Guide describes information about the DataBlade® API, the C-language application programming interface (API) provided with HCL Informix®.
Database access
Execute SQL statementsOne basic task of a DataBlade® API module is to send SQL statements to the database server for execution.
Retrieving query data
Obtain column values
Access the columnsThe mi_value() and mi_value_by_name() functions access the row structure for the current row. The current row is in the cursor that is associated with the current statement. Because a current statement is associated with a connection, you must pass a connection descriptor into mi_value() or mi_value_by_name() to identify the row to access.
Interpret column-value statusThe mi_value() and mi_value_by_name() functions return a value status, which identifies how to interpret the column value that these functions pass back.

Interpret column-value status

The mi_value() and mi_value_by_name() functions return a value status, which identifies how to interpret the column value that these functions pass back.

The following table shows the kinds of column values that these functions can identify.


Type of column value	Value-status constant	More information
A built-in, opaque, or distinct data type	MI_NORMAL_VALUE	Obtain normal values
An SQL NULL value	MI_NULL_VALUE	Obtain NULL values
A row type	MI_ROW_VALUE	Obtain row values
A collection	MI_COLLECTION_VALUE	Obtain collection values

You can use a switch statement based on these value-status constants to determine how to handle the column value.

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