Special function 

There are certain special functions that are not restricted to specific data types.

Syntax

<special_function> ::=
  VALUE    ( <expression>, <expression>,...)
| GREATEST ( <expression>, <expression>,...)
| LEAST    ( <expression>, <expression>,...)
| DECODE   ( <check_expression>, <search_and_result_spec>,...[, <default_expression> ] )

expression, check_expression, search_and_result_spec, default_expression

VALUE(x,y,...), GREATEST(x,y,...), LEAST(x,y,...), DECODE(x,y,...,z)