Use two temporary tables to assign "color" to data results

Question

Hi, Everyone... Here's a rundown of what I'm trying to do, any help is obviously appreciated...
Example Tables and Data:
I have 5 Courses, each course has 2 assignments.
with Courses as (
select 100 courseID from dual union all
select 200 from dual union all
select 300 from dual union all
select 400 from dual union all
select 500 from dual
), Assigns as (
select 'test100' name, 100 courseID from dual union all
select 'test100', 100 from dual union all
select 'test200', 200 from dual union all
select 'test200', 200 from dual union all
select 'test300', 300 from dual union all
select 'test300', 300 from dual union all
select 'test400', 400 from dual union all
select 'test400', 400 from dual union all
select 'test500', 500 from dual union all
select 'test500', 500 from dual
select assigns.name, assigns.courseID from courses
inner join assigns on assigns.courseID = courses.courseIDI need each assignment to get a color assigned to it according to it's courseID. So my theory is that I'd have a temporary table with a list of colors; each courseID would get assigned a color but my question is how do I assign each courseID a color without anything to join the temporary table on? Once each courseID has a color, I'd join in Assigns so that each assignment has a color associated with it according to it's courseID.
--Color table with 6 colors
with Colors as (
select 'red' color from dual union all
select 'blue' from dual union all
select 'yellow' from dual union all
select 'green' from dual union all
select 'purple' from dual union all
select 'teal' from dual
)I have a previous post about this but I didn't explain it well and to link to it would probably add confusion to this question... happy to delete that post if someone recommends it.
Thanks for any help! Running Oracle 11g.

Answer 1

Hi,
939920 wrote:
I don't have the ability to store the courseID with the colors...Then get it, or have someone with the ability make the change for you.
Is the problem that you have more than 6 courses, but you want to color-code them with only 6 colors, and there's no telling which courses may be included in the results of a given query?
If so, you can do somehting like this:
WITH     colors     AS
     SELECT  'red' AS color_name     FROM dual UNION ALL
     SELECT  'blue'                FROM dual UNION ALL
     SELECT      'yellow'          FROM dual UNION ALL     
     SELECT     'green'               FROM dual UNION ALL
     SELECT  'purple'          FROM dual UNION ALL
     SELECT     'teal'                FROM dual
,     colors_plus     AS
     SELECT     color_name
     ,     ROW_NUMBER () OVER (ORDER BY NULL) - 1     AS color_id
     ,     COUNT (*)     OVER ()                    AS color_cnt
     FROM     colors
,     course_assigns     AS
     SELECT  a.name
     ,     a.courseid
     ,     DENSE_RANK () OVER (ORDER BY  a.courseid)     AS course_num
     FROM          assigns          a
     INNER JOIN      courses      c     ON   a.courseid   = c.courseid     -- If needed
SELECT     ca.name
,     ca.courseid
,     cp.color_name
FROM     course_assigns  ca
JOIN     colors_plus       cp  ON   cp.color_id  = MOD ( ca.course_num
                                             , cp.color_cnt
;Typical output:
AME      COURSEID COLOR_
test100        100 blue
test100        100 blue
test200        200 yellow
test200        200 yellow
test300        300 green
test300        300 green
test400        400 purple
test400        400 purple
test500        500 teal
test500        500 tealIt would be better if you could create a real table like colors_plus.
If there are more than 6 distinct courses in the output, then 2 or more courses may be coded with the same color, but no color will be used N times (N>1) until all colors have been used N-1 times.
The assignment of courses to coolors is arbitrary. Depending on how fancy you want to make this, you might want to do something more complicated. For example, say you have 2 courses with 10 rows each, and 5 courses with 1 row each. The query above will have to assign the same color to 2 differenct courses, and it might assign the color 'blue' to the 2 courses with 10 rows each. The query above can be modified, if necessary, to assign the colors in order of frequency, to guarantee that the two 10-row courses get different colors, and that the colors are more evenly distibuted in general. I'll leave this as an execise. (Hint: use the frequency in the ORDER BY clause of DENSE_RANK. To get the frequency, use the analytic COUNT function in a sub-query. Why do you need a sub-query? Discuss amongst yourselves.)