Question

I have two tables like this:

    ---------        - -----------
    - X - Y -        - X - VALUE -
    ---------        - -----------
    -x1 - y1-        - x1- value1-     
    -x2 - y2-        - x1- value2-     
    -x3 - y3-        - x2- value3-     
    ---------        - x3- value4-
                     - x3- value5-
                     - x3- value6-
                     -------------

I want join them like this:

    -----------------
    - X - Y - VALUE -
    -----------------
    -x1 - y1- value1-
    -   -   - value2-
    -x2 - y2- value3-
    -x3 - y3- value4-
    -   -   - value5-
    -   -   - value6-
    -----------------

I dont want to duplicate X values.

Can anybody show this query or give reference to somebodys example?

thanks!

Answer 1

It seems that you are trying to remove the X, Y values after the first occurrence. You can do this with most databases, using the row_number() function. I am calling the first table XY and the second table X

select (case when seqnum = 1 then x end) as x,
       (case when seqnum = 1 then y end) as y,
       value
from (select xy.*, x.value,
             row_number() over (partition by xy.x order by xy.value) as seqnum
      from X join
           XY
           on x.x = xy.x
order by x, y