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From "Thomas Fischer (JIRA)" <j...@apache.org>
Subject [jira] Commented: (TORQUE-60) MySQL left joins may lead to "ERROR 1054: Unknown column ... in on clause"
Date Thu, 19 Oct 2006 07:46:37 GMT
    [ http://issues.apache.org/jira/browse/TORQUE-60?page=comments#action_12443437 ] 
            
Thomas Fischer commented on TORQUE-60:
--------------------------------------

Can you check if  the following works:

criteria.addJoin(APeer.ID, BPeer.ID, Criteria.INNER_JOIN);
criteria.addJoin(APeer.ID, CPeer.ID, Criteria.LEFT_JOIN);


>From the Torque documentation
http://db.apache.org/torque/releases/torque-3.2/runtime/reference/read-from-db.html#Inner_joins_for_qualifying

<Torque docs>
Also, in SQL, there are two different ways to state an inner join. The first way is a statement
like

SELECT BOOK.* FROM BOOK INNER JOIN AUTHOR ON BOOK.AUTHOR_ID=AUTHOR.AUTHOR_ID

SQL like this is produced if the join type is stated explicitly (as above).
The second way to create an inner join is

SELECT BOOK.* FROM BOOK,AUTHOR WHERE BOOK.AUTHOR_ID=AUTHOR.AUTHOR_ID

A SQL statement like this is created by not supplying the join type, for example in

criteria.addJoin(AuthorPeer.AUTHOR_ID, BookPeer.AUTHOR_ID);

Note that both SQL statements return the same result set.
It is not possible to combine both ways of creating a join in most databases, i.e. code like

criteria.addJoin(AuthorPeer.AUTHOR_ID, BookPeer.AUTHOR_ID);
criteria.addJoin(BookPeer.PUBLISHER_ID, PublisherPeer.PUBLISHER_ID, Criteria.INNER_JOIN);

produces an SQL error in most databases. In most circumstances, it is recommended to state
t the join type explicitly. However, if the "INNER JOIN" syntax is not supported by your database,
try not to state the join type explicitly.
</Torque docs>

> MySQL left joins may lead to "ERROR 1054: Unknown column ... in on clause"
> --------------------------------------------------------------------------
>
>                 Key: TORQUE-60
>                 URL: http://issues.apache.org/jira/browse/TORQUE-60
>             Project: Torque
>          Issue Type: Bug
>          Components: Runtime
>    Affects Versions: 3.2
>         Environment: MySQL 5.0.x (where x >= 15)
>            Reporter: Stefan Broetz
>
> I have three tables A, B, and C, each of them having an ID and DATA column. Now I want
to inner join A and B on their ids and left outer join A and C on their ids. Using
> Criteria criteria = new Criteria();
> criteria.addJoin(APeer.ID, BPeer.ID);
> criteria.addJoin(APeer.ID, CPeer.ID, Criteria.LEFT_JOIN);
> [...]
> BasePeer.doSelect(criteria);
> gives me the MySQL error 1054: "Unknown column 'a.ID' in 'on clause'. The problem is
the generated SQL statement:
> SELECT ... FROM a, b LEFT JOIN c ON a.id = c.id WHERE a.id = b.id ...
> According to the SQL:2003 standard this means that only tables B and C are joined and
a.id is neither a column in B nor in C. If you want to join tables A and C, your SQL statement
has either to look like this
> SELECT ... FROM b, a LEFT JOIN c ON a.id = c.id WHERE a.id = b.id ...
> (notice that I swapped a and b in the FROM clause) or like this
> SELECT ... FROM (a, b) LEFT JOIN c ON a.id = c.id WHERE a.id = b.id ...
> I guess the latter is what you usually want to have. So the solution might simply be
the introduction of parantheses around the FROM clause.
> See also http://bugs.mysql.com/bug.php?id=13551

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