Question

Is it possible to create a table with a column that combines two column values?
something like this:

create table test1
(
number1 decimal(6,2),
number2 decimal(6,2),
total decimal(6,2) DEFAULT (number1+number2)
);

Answer 1

You can do this using a trigger:

create table test1
  (number1 decimal(6,2),
   number2 decimal(6,2),
   total decimal(6,2));

CREATE TRIGGER test1_bi
  BEFORE INSERT ON test1
  FOR EACH ROW
BEGIN
  IF :new.total is NULL THEN
    :NEW.TOTAL := :new.number1 + :new.number2;
  END IF;
END test1_bi;

INSERT INTO test1(number1, number2) VALUES(1, 2);

SELECT * FROM test1;

After the SELECT you’ll find that TOTAL has a value of 3, as expected.

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