Function (function_spec) 
There is a series of functions (function_spec) that can be applied to a value (row) as an argument and supply a result. These functions (predefined and user defined) and their calls are introduced in the following sections.
Structure
Syntax
<function_spec> ::= <arithmetic_function> | <conversion_function> | <date_function> | <dbfunction_call> | <extraction_function> | <special_function> | <string_function> | <time_function> | <trigonometric_function>
End of the code.
Examples
SQL Tutorial, Functions
Explanation
The arguments and results of the functions are numeric, alphanumeric or Boolean values that are subject to certain restrictions. LOB columns are not allowed as arguments, with the exception of those explicitly stated.