SQL query for all combinations without repetition

oracle

I need a function for calculating combinations without repetition from a list.

Example:
I have a list of names e.g.

Tom
Bob
Paul
Tina

Now I need a list of 3 names out of the 4 without having a name twice and without having the 3 names twice because of ordering. The correct result would be 

Tom,Bob,Paul
Tom,Paul,Tina
Tom,Bob,Tina
Bob,Paul,Tina

Of course this also should work quite fast with 14 out of 19 or similar.

Best Answer

You can use regular joins:

SQL> WITH DATA AS
  2   (SELECT 'Tom' NAME
  3      FROM dual
  4    UNION ALL
  5    SELECT 'Bob' NAME
  6      FROM dual
  7    UNION ALL
  8    SELECT 'Paul' NAME
  9      FROM dual
 10    UNION ALL
 11    SELECT 'Tina' NAME
 12      FROM dual)
 13  SELECT *
 14    FROM DATA d1
 15    JOIN DATA d2 ON d1.name > d2.name
 16    JOIN DATA d3 ON d2.name > d3.name;

NAME NAME NAME
---- ---- ----
Tom  Tina Bob
Tom  Tina Paul
Tom  Paul Bob
Tina Paul Bob
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