我有关于 Hibernate ManyToOne 关联的问题。
我有一个像这样映射的产品实体:
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;
}
那么你怎么能看到我们与 ProductCategory 表有关系呢？我们将 FK 存储在 Product 表中。
当我创建按特定类别和价格选择产品的查询时，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 ?
我的下一个问题是:如何避免两个表的内部联接:Product 和 ProductCategory？
我的 Criteria DAO 代码:
criteria.createAlias("category", "cat");
criteria.add(Restrictions.conjunction()
.add(Restrictions.between("salePrice", priceLow, priceHigh))
.add(Restrictions.in("cat.id", categoryIds)));
谢谢。
最佳答案
线路
criteria.createAlias("category", "cat");
准确的意思是:创建与 Category 实体的内部联接。
直接使用
criteria.add(
Restrictions.conjunction()
.add(Restrictions.between("salePrice", priceLow, priceHigh))
.add(Restrictions.in("category.id", categoryIds)));
关于SQL 查询中的 Hibernate ManyToOne 关联和连接表，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/11395662/