sql - Selecting distinct values for multiple columns

Question

I have a table where many pieces of data match to one in another column, similar to a tree, and then data at the 'leaf' about each specific leaf

eg

Food Group      Name       Caloric Value  
Vegetables      Broccoli   100  
Vegetables      Carrots    80    
Fruits          Apples     120  
Fruits          Bananas    120  
Fruits          Oranges    90

I would like to design a query that will return only the distinct values of each column, and then nulls to cover the overflow

eg

Food group    Name     Caloric Value  
Vegetables    Broccoli 100  
Fruit         Carrots  80  
              Apples   120  
              Bananas  90  
              Oranges   

I'm not sure if this is possible, right now I've been trying to do it with cases, however I was hoping there would be a simpler way

Answer 1

Seems like you are simply trying to have all the distinct values at hand. Why? For displaying purposes? It's the application's job, not the server's. You could simply have three queries like this:

SELECT DISTINCT [Food Group] FROM atable;

SELECT DISTINCT Name FROM atable;

SELECT DISTINCT [Caloric Value] FROM atable;

and display their results accordingly.

But if you insist on having them all in one table, you might try this:

WITH atable ([Food Group], Name, [Caloric Value]) AS (
  SELECT 'Vegetables', 'Broccoli', 100  UNION ALL
  SELECT 'Vegetables', 'Carrots',  80   UNION ALL
  SELECT 'Fruits',     'Apples',   120  UNION ALL
  SELECT 'Fruits',     'Bananas',  120  UNION ALL
  SELECT 'Fruits',     'Oranges',  90   
),
atable_numbered AS (
  SELECT
    [Food Group], Name, [Caloric Value],
    fg_rank = DENSE_RANK() OVER (ORDER BY [Food Group]),
    n_rank  = DENSE_RANK() OVER (ORDER BY Name),
    cv_rank = DENSE_RANK() OVER (ORDER BY [Caloric Value])
  FROM atable
)
SELECT
  fg.[Food Group],
  n.Name,
  cv.[Caloric Value]
FROM (
  SELECT fg_rank FROM atable_numbered  UNION
  SELECT n_rank  FROM atable_numbered  UNION
  SELECT cv_rank FROM atable_numbered
) r (rank)
  LEFT JOIN (
    SELECT DISTINCT [Food Group], fg_rank
    FROM atable_numbered) fg ON r.rank = fg.fg_rank
  LEFT JOIN (
    SELECT DISTINCT Name, n_rank
    FROM atable_numbered) n  ON r.rank = n.n_rank
  LEFT JOIN (
    SELECT DISTINCT [Caloric Value], cv_rank
    FROM atable_numbered) cv ON r.rank = cv.cv_rank
ORDER BY r.rank