Need Help with Creating the SQl query

Question

Hi,
SQL query gurus...
INFORMATION:
I have two table, CURRENT and PREVIOUS.(Table Defs below).
CURRENT:
Column1 - CURR_PARENT
Column2 - CURR_CHILD
Column3 - CURR_CHILD_ATTRIBUTE 1
Column4 - CURR_CHILD_ATTRIBUTE 2
Column5 - CURR_CHILD_ATTRIBUTE 3
PREVIOUS:
Column1 - PREV_PARENT
Column2 - PREV_CHILD
Column3 - PREV_CHILD_ATTRIBUTE 1
Column4 - PREV_CHILD_ATTRIBUTE 2
Column5 - PREV_CHILD_ATTRIBUTE 3
PROBLEM STATEMENT
Here the columns 3 to 5 are the attributes of the Child. Lets assume that I have two loads, One Today which goes to the CURRENT table and one yesterday which goes to the PREVIOUS table. Between these two loads there is a CHANGE in the value for Columns either 3/4/5 or all of them(doesnt matter if one or all).
I want to determine what properties for the child have changed with the help of a MOST efficient SQL query.(PARENT+CHILD is unique key). The Database is ofcourse ORACLE.
Please help.
Regards,
Parag

Answer 1

Hi,
The last message was not posted by the same user_name that started the thread.
Please don't do that: it's confusing.
Earlier replies give you the information you want, with one row of output (maximum) per row in current_tbl. There may be 1, 2 or 3 changes on a row.
You just have to unpivot that data to get one row for every change, like this:
WITH     single_row  AS
     SELECT     c.curr_parent
     ,     c.curr_child
     ,     c.curr_child_attribute1
     ,     c.curr_child_attribute2
     ,     c.curr_child_attribute3
     ,     DECODE (c.curr_child_attribute1, p.prev_child_attribute1, 0, 1) AS diff1
     ,     DECODE (c.curr_child_attribute2, p.prev_child_attribute2, 0, 2) AS diff2
     ,     DECODE (c.curr_child_attribute3, p.prev_child_attribute3, 0, 3) AS diff3
     FROM     current_tbl    c
     JOIN     previous_tbl   p     ON  c.curr_parent     = p.prev_parent
                            AND c.curr_child     = p.prev_child
     WHERE     c.curr_child_attribute1     != p.prev_child_attribute1
     OR     c.curr_child_attribute2     != p.prev_child_attribute2
     OR     c.curr_child_attribute3     != p.prev_child_attribute3
,     cntr     AS
     SELECT     LEVEL     AS n
     FROM     dual
     CONNECT BY     LEVEL <= 3
SELECT     s.curr_parent     AS parent
,     s.curr_child     AS child
,     CASE     c.n
          WHEN  1  THEN  s.curr_child_attribute1
          WHEN  2  THEN  s.curr_child_attribute2
          WHEN  3  THEN  s.curr_child_attribute3
     END          AS attribute
,     c.n          AS attribute_value
FROM     single_row     s
JOIN     cntr          c     ON     c.n IN ( s.diff1
                                , s.diff2
                                , s.diff3
ORDER BY  attribute_value
,            parent
,            child
;