Datatype conversions change an expression from one datatype to another and reformat date and time information. Adaptive Server provides three datatype conversion functions, convert, inttohex, and hextoint.
Adaptive Server performs certain datatype conversions automatically. These are called implicit conversions. For example, if you compare a char expression and a datetime expression, or a smallint expression and an int expression, or char expressions of different lengths, Adaptive Server automatically converts one datatype to another. Another example, when a datetime value is converted to a date value, the time portion will be truncated leaving only the date portion. If a time value is converted to a datetime value, a default date portion of Jan 1, 1900 will be added to the new datetime value. If a date value is converted to a datetime value, a default time portion of 00:00:00:000 will be added to the datetime value.
You must request other datatype conversions explicitly, using one of the built-in datatype conversion functions. For example, before concatenating numeric expressions, you must convert them to character expressions. If you attempt to explicitly convert a date to a datetime and the value is outside the datetime range such as “Jan 1, 1000” the conversion is not allowed and an error message is given.
Adaptive Server does not allow you to convert certain datatypes to certain other datatypes, either implicitly or explicitly. For example, you cannot convert smallint data to datetime or datetime data to smallint. Unsupported conversions result in error messages.
