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Extending Informix-Universal Server: Data Types
Chapter 3: Creating User-Defined Casts
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 A cast is a mechanism that converts a value from one data type to another data type. Casts allow you to make comparisons between values of different data types or substitute a value of one data type when another data type is expected.

To convert a value of one data type to another data type, the database server must have a cast that describes how to perform this conversion. Universal Server supports two kinds of cast:

    A system-defined cast is a cast that is built into the database server. A system-defined cast performs an automatic conversion between two built-in data types.

    A user-defined cast is a cast that you define to provide data conversion between two non-built-in data types.

For more information on system-defined casts, see the chapter on data types in the Informix Guide to SQL: Reference. This chapter describes how to create user-defined casts for data types in a database.



Extending Informix-Universal Server: Data Types, version 9.1
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