ARRAY_MAX takes an array expression as an argument and returns an element value that represents the maximum value of all the elements composing the array. If you specify a scope reference, the function is applied only to the elements within the limits of the given scope.
The affected elements cannot be filtered through a conditional expression. Therefore, a SELECT statement involving ARRAY_MAX must not contain an array relational expression in the WHERE clause.
If a NULL element is encountered in the array argument, it is ignored and not considered when doing the calculation. If the array argument contains any elements that is in an uninitialized state, an error is returned. Use a scope reference to avoid referencing a range of the array with uninitialized elements, or set any uninitialized elements to NULL. You can do this with the OEXTEND method. See OEXTEND.
If array_expr is NULL, the function returns NULL.