LEFT OUTER JOIN with CONNECT_BY_ROOT

Question

I've got

SELECT 
  CONNECT_BY_ROOT TAXY.IDCATEGORY AS IDBRANCH
  , TAXY.IDCATEGORY
  , TAXY.IDPARENTCATEGORY
  , TAXY.IDCONTENT
  , TAXY.CATEGORYNAME
  , LEVEL AS LVL
FROM TAXONOMY TAXY
CONNECT BY TAXY.IDCATEGORY = PRIOR TAXY.IDPARENTCATEGORY

and want to add to each entry CONTENTNAME column from table CONTENT.

I've tried:

SELECT 
  CONNECT_BY_ROOT TCT.CONTENTNAME AS ENDNODECONTENTNAME
  , TAXY.IDCATEGORY
  , TAXY.IDPARENTCATEGORY
  , TAXY.IDCONTENT
  , TCT.CONTENTNAME 
  , TAXY.CATEGORYNAME
  , LEVEL AS LVL
FROM TAXONOMY TAXY
LEFT OUTER JOIN CONTENT TCT ON TCT.IDCONTENT = TAXY.IDCONTENT
CONNECT BY TAXY.IDCATEGORY = PRIOR TAXY.IDPARENTCATEGORY

Expecting the same results, only with CONNECT_BY_ROOT using 1 extra column: CONTENTNAME from CONTENT, associated by IDCONTENT; which should be NULL if there is no associated content (IDCONTENT is NULL)

Instead I only get the rows where IDCONTENT is not NULL. What can I do to get those rows too?

I've also tried:

SELECT 
  CONNECT_BY_ROOT TAXY.IDCATEGORY AS IDBRANCH
  , TAXY.IDCATEGORY
  , TAXY.IDPARENTCATEGORY
  , TAXY.IDCONTENT
  , TCT.CONTENTNAME 
  , TAXY.CATEGORYNAME
  , LEVEL AS LVL
FROM TAXONOMY TAXY
LEFT OUTER JOIN CONTENT TCT ON TCT.IDCONTENT = TAXY.IDCONTENT
CONNECT BY TAXY.IDCATEGORY = PRIOR TAXY.IDPARENTCATEGORY

And I've also tried

SELECT 
  SYS_CONNECT_BY_PATH(TAXY.CATEGORYNAME, ' \ ') AS BREADCRUMBSPATH
  , TAXY.IDCATEGORY
  , TAXY.IDPARENTCATEGORY
  , TAXY.IDCONTENT
  , TCT.CONTENTNAME 
  , TAXY.CATEGORYNAME
  , LEVEL AS LVL
FROM TAXONOMY TAXY
LEFT OUTER JOIN CONTENT TCT ON TCT.IDCONTENT = TAXY.IDCONTENT
START WITH TAXY.IDPARENTCATEGORY IS NULL CONNECT BY TAXY.IDPARENTCATEGORY = PRIOR TAXY.IDCATEGORY

but I get the same results (only values where IDCONTENT is not NULL)

The most weird of it all is that the query was working as expected yesterday on development DB and now it is not. So I've created a fiddle to check if I could reproduce previous results and it works fine... http://sqlfiddle.com/#!4/ecb9d/1 http://sqlfiddle.com/#!4/ecb9d/3

What could have caused this change of behavior?

Answer 1

I still don't know what happened (still not working) but this solution seems to work fine in both cases:

SELECT IDBRANCH, ENDNODEIDCONTENT, IDCATEGORY, IDPARENTCATEGORY, TAXYJ.IDCONTENT, TCT.CONTENTNAME AS ENDNODECONTENTNAME, CATEGORYNAME, LVL
FROM (
  SELECT CONNECT_BY_ROOT TAXY.IDCATEGORY AS IDBRANCH
  , CONNECT_BY_ROOT TAXY.IDCONTENT AS ENDNODEIDCONTENT
  , TAXY.IDCATEGORY
  , TAXY.IDPARENTCATEGORY
  , TAXY.IDCONTENT
  , TAXY.CATEGORYNAME
  , LEVEL AS LVL
FROM TAXONOMY TAXY
CONNECT BY TAXY.IDCATEGORY = PRIOR TAXY.IDPARENTCATEGORY
) TAXYJ 
LEFT OUTER JOIN CONTENT TCT ON TCT.IDCONTENT = TAXYJ.ENDNODEIDCONTENT

http://sqlfiddle.com/#!4/ecb9d/4