New J2EE stores: subselects

[Christopher Lenz <cm...@gmx.de>]

Hi Ashok and all...

I've been wondering about the sub-selects you're using for the new database 
schema. As far as I can tell, they're used to join between various tables and 
the URI table.

For example this:

SELECT URI_STRING
FROM URI
WHERE URI_ID IN (
  SELECT CHILD_URI_ID
  FROM CHILDREN
  WHERE URI_ID = 1
);

should result in this:
 URI_STRING
------------
/actions
/files
/users

If the root URI "/" has ID 1 and the only children are "/actions", "/files" and 
"/users". Right ?

Now, as sub-selects are not available for so popular MySQL, I've been trying to 
figure out how to avoid them. As I noted, the sub-selects are used for joins, so 
why not use actual joins instead, like this:

SELECT URI_STRING
FROM URI, CHILDREN
WHERE URI.URI_ID = CHILDREN.CHILD_URI_ID
  AND CHILDREN.URI_ID = 1

?

Should have the same result, and should be more obvious to the database system's 
query analyzer.

Or am I missing something ?

--
Christopher Lenz
_______________________________________________
 /=/ cmlenz at gmx.de





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