GREATEST/LEAST(x,y,...) 

GREATEST(x,y,...) or LEAST(x,y) is a special function that calculates the maximum or minimum value of all arguments (expressions).

The functions can be applied to any data type. The data types of the individual expressions must be comparable.

	Result of the function
At least one argument is the NULL value	NULL Value
At least one argument is the special NULL value	Special NULL value

Examples

SQL Tutorial, Information About Character Strings