MySQL left joins may lead to "ERROR 1054: Unknown column ... in on clause"
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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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