GREATEST
                                                            Purpose
This function returns the largest of the specified expressions.
Syntax
greatest::=
                                                                        
                                                                    
Usage Notes
- 
                                                                    
The data type
BOOLEANis not supported. - 
                                                                    
If one of the arguments is
NULL, the function returnsNULL. 
Example
SELECT GREATEST(1,5,3) GREATEST;