Select records based on column priority

Question

First of all, the title of this question is horrible, but I didn\'t find a better way to describe my issue.

There\'s probably a very easy way to do this, but I couldn\'t

Answer 1

You can have it like this

WITH PriorityTable
AS
(
    SELECT T.*,
        ROW_NUMBER() OVER (PARTITION BY T.ID
                            ORDER BY PT.ColorPriority )  PriorityColumn
    FROM XX AS T
    INNER JOIN (
        SELECT 'RED' AS f_COLOUR , 1 AS ColorPriority
        UNION
        SELECT 'GREEN' AS f_COLOUR , 2 AS ColorPriority
    ) AS PT
        ON T.f_COLOUR  = PT.f_COLOUR 
)

SELECT * FROM PriorityTable
WHERE PriorityColumn = 1

Answer 2

Your query is nearly correct. Just use PRODUCTID and not ID.

SELECT * 
FROM xx
WHERE f_COLOUR = "GREEN"
UNION
SELECT * 
FROM xx 
WHERE PRODUCTID not in 
                (SELECT PRODUCTID
                 FROM xx 
                 WHERE f_COLOUR = "GREEN");

SQLFiddle Demo

Answer 3

I just want to offer that you can do this with a group by:

select (case when sum(case when colour = 'Green' then 1 else 0 end) > 0
             then max(case when colour = 'Green' then id end)
             else max(case when colour = 'Red' then id end)
        end) as id,
       product_id
       (case when sum(case when colour = 'Green' then 1 else 0 end) > 0 then 'Green'
             else 'Red'
        end) as colour
from t
group by product_id

Answer 4

Try this

SELECT * 
FROM xx
WHERE COLOUR = 'GREEN'
UNION
SELECT * 
FROM xx WHERE P_Id not in 
                (SELECT P_Id
                 FROM Persons 
                 WHERE COLOUR = 'GREEN');

See ALSO SQL FIDDLE DEMO