Re: constrains on two tables

In response to finecur <finecur(at)yahoo(dot)com>:

> On Sep 10, 9:55 pm, finecur <fine(dot)(dot)(dot)(at)yahoo(dot)com> wrote:
> > Hi
> >
> > Here is my table:
> >
> > Table School
> > (
> > id integer,
> > name text
> > );
> >
> > Table Department
> > (
> > id integer,
> > school_id integer reference school(id),
> > name text
> > );
> >
> > Table Course
> > (
> > department_id integer references department(id),
> > name text,
> > course_number text
> > )
> >
> > I would like to make the course_number unique, but not in the course
> > table, nor in department. I would like to make the course_number
> > unique in the scope of School. So, you may see the same course_number
> > in Course table, but (school_id, course_number) should be always
> > unique. How can I make the constrain?

ALTER TABLE Course PRIMARY KEY(school_id, course_number);

and add the school_id column to the Course table.

--
Bill Moran
http://www.potentialtech.com