GREATEST
The GREATEST function returns the largest expression in a list of expressions. All expressions after the first are implicitly converted to the data type of the first expression before the comparison.
To retrieve the smallest expression in a list of expressions, use LEAST.
Return Value
The data type of the first expression.
Syntax
GREATEST (expr [, expr]...)
Arguments
 expr

An expression.
Examples
Example 7104 Finding the the Text Expression that is Last Alphabetically
The following statement selects the string that is last in alphabetic sequence.
SHOW GREATEST ('Harry', 'Harriot', 'Harold')
Harry
Example 7105 Finding the Largest Numerical Expression
The following statement selects the number with the greatest value.
SHOW GREATEST (5, 3, 18)
18