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Question

I am having difficulty figuring out how to implement a before insert trigger using a cursor that will compare the insert number with the max value of the 1 column table (NUM) , then print out the corresponding message. Any help would be greatly appreciated.

create or replace trigger MAXSOME
  before insert on SOMENUMBERS for each row
declare
  cursor pointer is 
    select max(NUM) from SOMENUMBERS;

  x number;
begin
    x := :new.NUM;

    if x > pointer.num then
        dbms_output.put_line('The new number ' || x || ' is greater than the greatest number in the table.');
    elsif x := pointer then
        dbms_output.put_line('The new number ' || x || ' is the same as the greatest number in the table.');
    else
       dbms_output.put_line(pointer.num || ' is still the largest number in the table.'); 
    end if;
end;
/

Answer 1

If you declare a cursor you have to open it in a loop but you don't even need a cursor. Using dbms_output is not going to work very well as one session may insert and you may be waiting for the output using another session.. Create another table and log the output there.
I see Knuckles suggests an autonomous transaction but my test case succeeded without one.

create or replace trigger MAXSOME
before insert on SOMENUMBERS
for each row
declare

    x SOMENUMBERS.NUM%TYPE;
begin
    select max(NUM) into x from SOMENUMBERS;


    if x > :new.NUM then
        dbms_output.put_line('The new number ' || :new.NUM || ' is greater than the greatest number in the table.');
    elsif x = :new.NUM then
        dbms_output.put_line('The new number ' || :new.NUM || ' is the same as the greatest number in the table.');
    else
       dbms_output.put_line(:new.NUM || ' is still the largest number in the table.'); 
    end if;
end;