我对Hibernate ManyToOne关联有疑问。
我有一个像这样映射的Product实体：
public class Product {
@Id
@DocumentId
@Column(name = "PRODUCT_ID", columnDefinition = "integer")
@Index(name = "PRODUCT_ID_IDX")
private Long id;
@Column(name = "SALE_PRICE")
@Index(name = "PRODUCT_PRICE_IDX")
private Double salePrice;
...
@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "CATEGORY_ID", nullable = true)
@Index(name = "PRODUCT_ID_CATEGORY_IDX")
private ProductCategory category;
}
那你怎么看我们与ProductCategory表有关系呢？而FK我们存储在Product表中。
当我创建查询时，按特定类别和价格选择产品我有下一个SQL：
select
this_.PRODUCT_ID as PRODUCT1_9_1_,
this_.BUY_URL as BUY2_9_1_,
this_.CATEGORY_ID as CATEGORY15_9_1_,
this_.CURRENCY as CURRENCY9_1_,
this_.IMAGE_URL as IMAGE4_9_1_,
this_.INSTOCK as INSTOCK9_1_,
this_.LONG_DESCRIPTION as LONG6_9_1_,
this_.NAME as NAME9_1_,
this_.RATING as RATING9_1_,
this_.RETAIL_PRICE as RETAIL9_9_1_,
this_.SALE_PRICE as SALE10_9_1_,
this_.SHIPPING as SHIPPING9_1_,
this_.SHORT_DESCRIPTION as SHORT12_9_1_,
this_.UPC as UPC9_1_,
this_.VIEWS as VIEWS9_1_,
cat1_.CATEGORY_ID as CATEGORY1_10_0_,
cat1_.NAME as NAME10_0_,
cat1_.RATING as RATING10_0_,
cat1_.VIEWS as VIEWS10_0_,
cat1_.VISIBLE as VISIBLE10_0_
from
PRODUCT this_
inner join
PRODUCT_CATEGORY cat1_
on this_.CATEGORY_ID=cat1_.CATEGORY_ID
where
(
this_.SALE_PRICE between ? and ?
and cat1_.CATEGORY_ID in (
?
)
)
order by
this_.NAME asc limit ? offset ?
我的问题是：如何避免两个表的内连接：Product和ProductCategory？
我的标准DAO代码：
criteria.createAlias("category", "cat");
criteria.add(Restrictions.conjunction()
.add(Restrictions.between("salePrice", priceLow, priceHigh))
.add(Restrictions.in("cat.id", categoryIds)));
感谢。
答案 0 :(得分：2)
该行
criteria.createAlias("category", "cat");
正是指：使用Category实体创建内部联接。
只需使用
criteria.add(
Restrictions.conjunction()
.add(Restrictions.between("salePrice", priceLow, priceHigh))
.add(Restrictions.in("category.id", categoryIds)));