Ordered Value by Column / Row

Question

Its a little difficult to explain. It might be easier to skip to the examples.

A table has an id and four columns that each allow null.

ID, Col1, Co         


        

Answer 1

Use:

SELECT DISTINCT COL1 AS col
  FROM YOUR_TABLE
 WHERE col1 IS NOT NULL
UNION
SELECT DISTINCT COL2 AS col
  FROM YOUR_TABLE
 WHERE col2 IS NOT NULL
UNION 
SELECT DISTINCT COL3 AS col
  FROM YOUR_TABLE
 WHERE col3 IS NOT NULL
UNION
SELECT DISTINCT COL4 AS col
  FROM YOUR_TABLE
 WHERE col4 IS NOT NULL
ORDER BY col

UNION will remove duplicates between the statements; DISTINCT will return a unique list of values per statement. UNION ALL would be faster than UNION, but it doesn't remove duplicates.