I have a table called **questions** containing a single column filled with Exam question IDs. Let's say:

```
Q1
Q2
Q2
...
Qn

```

Now I'd like to pick all the combinations of three questions, something like:

```
1, 2, 3
...
2, 5, 6
4, 7, 1
...
9, 6, 8

```

And seclect a subset of them made of rows that have globally unique values only. In the previous case:

```
1, 2, 3
9, 6, 8

```

Because the other two records contain 2 and 1 which are both contained in the (1, 2, 3) record.

How can this be achieved in SQL? The purpose is to create, let's say, 8 exams made of questions that are all different by each other.