Question

I have a table that looks like this:

| ID |  Order  | ... | Colour  |
|  1 |    A    | ... |   xxx   |
|  2 |    A    | ... |   xxx   |
|  3 |    A    | ... |   xxx   |
|  4 |    B    | ... |   xxx   |
|  5 |    B    | ... |   xxx   |
|  6 |    C    | ... |   xxx   |
|  7 |    A    | ... |   xxx   |
|  8 |    B    | ... |   xxx   |
|  9 |    B    | ... |   xxx   |
| 10 |    B    | ... |   xxx   |

I need to assign each order its own color and return the value. Unfortunately I dont know what the order name will be so I can’t do a simple CASE statement.

My question is, what would be the best, most efficient way to do this so that the results look something like this:

| ID |  Order  | ... | Colour   |
|  1 |    A    | ... |   Red    |
|  2 |    A    | ... |   Red    | 
|  3 |    A    | ... |   Red    |
|  4 |    B    | ... |   Blue   |
|  5 |    B    | ... |   Blue   |
|  6 |    C    | ... |   Green  |
|  7 |    A    | ... |   Red    |
|  8 |    B    | ... |   Blue   |
|  9 |    B    | ... |   Blue   |
| 10 |    B    | ... |   Blue    |

Many thanks for your help, I’ve been puzzling over this all day!

Answer 1

Without answers to the questions posted in the comments, I can’t be sure this is what you want. But, here goes…

DECLARE @paletteSize INT;

DECLARE @palette TABLE
    (    numVal INT IDENTITY(0, 1) PRIMARY KEY
        , colorVal VARCHAR(10)
    );

INSERT @palette
    ( colorVal )
VALUES 
    ( 'VIOLET' )
    ,( 'RED' )
    ,( 'BLUE' )
    ,( 'GREEN' )
    ,( 'ORANGE' )
    ,( 'YELLOW' );

SELECT @paletteSize = COUNT(*) FROM @palette;

DECLARE @source TABLE
    (    id INT IDENTITY(1, 1) PRIMARY KEY
        , orderVal CHAR(1)
    );
INSERT @source
    ( orderVal )
VALUES
    ( 'A' )
    ,( 'A' )
    ,( 'A' )
    ,( 'B' )
    ,( 'B' )
    ,( 'C' )
    ,( 'A' )
    ,( 'B' )
    ,( 'B' )
    ,( 'B');

SELECT
    sc.id
    , sc.orderVal
    , p.colorVal 
FROM 
    ( 
        SELECT 
            s.id
            , s.orderval
            , DENSE_RANK()
                OVER(    ORDER BY s.orderval ) % @paletteSize colorID
        FROM 
            @source s
    ) sc
JOIN 
    @palette p
    ON p.numVal = sc.colorID
ORDER BY 
    sc.id;

If your distinct Order values outnumber your Palette, it wraps around. You could also use NTILE instead of DENSE_RANK if you wanted to band orders into a set number of buckets to match your palette table’s count. The difference is in whether you want to cycle colors over values or group close values into a color.