如何将一组列限制为全为空或全为非空

Question

Lets say I have a table like so,

id | first name | middle name | last name

Now, the name columns can be NULL , but if any of the three, for example, first name is NOT NULL , then all three must be NOT NULL .

How can I enforce this in Oracle?

Answer 1

You can write a check constraint with the logics you need. For example:

alter table yourTable
  add constraint check_not_null check
    (   
        first_name  is not null and
        middle_name is not null and
        last_name   is not null
      OR
        first_name  is null and
        middle_name is null and
        last_name   is null
    );

Answer 2

Say,

alter table your_table 
  add constraint set_of_column_chk
  check (nvl2(first_name, 1, 0) + nvl2(middle_name, 1, 0) + nvl2(last_name, 1, 0) in (0, 3));