尝试在 Propel 2 中做一个相当简单的查询。我有一个 Person 表和一个 Possession 表 - 人们可以拥有许多财产,但每种财产类型只有一个。因此,一个人可以拥有 1 本书、1 辆汽车等。我正在尝试在 Propel 中编写一个查询,如果他们有车,它将返回所有人及其车名。这是代码和结果查询:
$x = PersonQuery::create()
->groupById()
->leftJoinPossession()
->addJoinCondition('Possession','Possession.possession_type = ?', 'car')
->withColumn('Possession.possession_name', 'CarName')
->where('Possession.possession_name IS NOT NULL')
->find()
->toString();
//resulting sql
SELECT person.id, possession.possession_name as CarName
FROM person
LEFT JOIN possession ON (person.id=possession.person_id AND possession.possession_type = 'car')
WHERE possession.possession_name IS NOT NULL;
这按预期工作。但是,我需要对拥有表进行多次连接(例如,获取每个人的书籍),因此我需要使用别名。以下是当我修改前面的查询以使用所有权表的别名(并且还为每个人获取书)时发生的情况:
$x = PersonQuery::create()
->groupById()
->leftJoinPossession('p')
->addJoinCondition('p','p.possession_type = ?', 'car')
->leftJoinPossession('p2')
->addJoinCondition('p2','p2.possession_type = ?', 'book')
->withColumn('p.possession_name', 'CarName')
->withColumn('p2.possession_name', 'BookName')
->where('p.possession_name IS NOT NULL')
->find()
->toString();
//resulting sql
SELECT person.id, p.possession_name as CarName, p2.possession_name as BookName
FROM person
CROSS JOIN possession
LEFT JOIN possession p ON (person.id=p.person_id AND p.possession_type = 'car')
LEFT JOIN possession p2 ON (person.id=p2.person_id AND p2.possession_type = 'book')
WHERE p.possession_name IS NOT NULL;
如您所见,出于某种原因,Propel 在查询中添加了“CROSS JOIN 占有”。这不会改变查询的结果,但会使其非常慢。关于如何告诉 Propel 在仍然为我的连接表使用别名的同时不要使用 CROSS JOIN 的任何想法?(如果我去掉 'where' 子句,CROSS JOIN 也会消失)