HQL Left Outer以一对一的关系连接空列

Question

左外连接应该从左表中获取所有数据,无论是否存在来自B表的匹配记录,但是如果左表right_id列为空,则不能获得记录.

我正在解释更多

在Data model:Order.java中,它是我的LEFT表,有一对一的关系

@OneToOne(targetEntity = OrderShippingDetail.class, optional=true, cascade = {CascadeType.ALL})
@JoinColumn(name = "SHIPPING_DETAIL_ID", referencedColumnName = "ID")
private OrderShippingDetail shippingDetail;

和HQL是:

    hql = "SELECT " +
            "o.id as id, " +
            "o.createTime as createTime, " +
            "o.customerEmailAddress as customerEmailAddress, " +
            "o.customerPhoneNumber as customerPhoneNumber, " +
            "o.customerNote as customerNote, " +
            "o.invoicePrintedFlag as invoicePrintedFlag, " +
            "shippingAddress.address.personName as shippingPersonName, " +
            "shippingDetail.shippingCompany.id as shippingCompanyId, "+
            "shippingDetail.shippingCompany.name as shippingCompanyName, "+
            "shippingDetail.receiptNumber as shippingReceiptNumber, "+
            "shippingDetail.trackingNumber as shippingTrackingNumber, "+
            "shippingDetail.price as shippingPrice, "+
            "o.invoiceNumber as invoiceNumber " + 
        "FROM Order AS o " +
        "LEFT OUTER JOIN o.shippingAddress AS shippingAddress " +
        "LEFT OUTER JOIN o.shippingDetail AS shippingDetail ";

但只有"SHIPPING_DETAIL_ID"不为空的记录.HQL有错误吗？它是通过建模SQL命令创建的,该命令是在hibernate运行时自动创建的.

我找到了这个,

HQL支持两种形式的关联连接:隐式和显式.

上一节中显示的查询都使用显式形式,即在from子句中显式使用join关键字的位置.这是推荐的表格.

隐式表单不使用join关键字.相反,使用点符号"解除引用"关联.隐式连接可以出现在任何HQL子句中.隐式连接导致生成的SQL语句中的内部联接.

我删除了SELECT部分​​中的点符号,所以我的新HQL:

hql = "SELECT " +
                "o.id as id, " +
                "o.createTime as createTime, " +
                "o.customerEmailAddress as customerEmailAddress, " +
                "o.customerPhoneNumber as customerPhoneNumber, " +
                "o.customerNote as customerNote, " +
                "o.invoicePrintedFlag as invoicePrintedFlag, " +
                "shippingDetail, " +
                "o.invoiceNumber as invoiceNumber " + 
            "FROM Order AS o " +
            "LEFT OUTER JOIN o.shippingAddress AS shippingAddress " +
            "LEFT OUTER JOIN o.shippingDetail AS shippingDetail ";

因此,它工作,它返回Order表中的所有记录,但是,我不想选择ShippingDetail对象中的所有列和关系.我该怎么做才能解决这个问题？

Answer 1

向查询添加另一个显式左连接:

SELECT o.id as id, 
...,
shippingCompany.id as shippingCompanyId, 
shippingCompany.name as shippingCompanyName, 
...
FROM Order AS o
LEFT OUTER JOIN o.shippingAddress AS shippingAddress 
LEFT OUTER JOIN o.shippingDetail AS shippingDetail
LEFT OUTER JOIN shippingDetail.shippingCompany AS shippingCompany