我有以下表格数据:
Product Reason Qty
Pepsi IN 10
Pepsi Out 2
Pepsi In 15
Pepsi Out 5
Coke IN 100
Coke Out 20
Coke In 35
Coke Out 25
Fanta Out 55
我想要得到如下结果:
Product Qty
Pepsi 18
Coke 90
Fanta -55
为此我得到了以下查询:
SELECT Product,
SUM(CASE WHEN reason IN ('IN','REFUND') THEN Qty
WHEN reason IN ('OUT','WASTE') THEN -Qty
ELSE NULL END) AS Qty
FROM stock
GROUP BY Product;
我想使用 JPA 规范
,就像 link 中使用的那样,我是JPA规范
的新手,有人可以指导我吗?
我有这个link还有这个link但我不确定解决问题的正确问题是什么?
编辑:
我尝试过以下代码
@Override
public Predicate toPredicate(Root<Stockdiary> root, CriteriaQuery<?> query, CriteriaBuilder builder) {
Path reasonexpression = root.get("reason");
Path qtyexpression = root.get("qty");
List<String> inList = new ArrayList<String> ();
inList.add("IN");
List<String> outList = new ArrayList<String> ();
outList.add("OUT");
Predicate inpredicate = reasonexpression.in(inList);
Predicate outpredicate = reasonexpression.in(outList);
Expression<Number> sum = builder.sum(
builder.<Number>selectCase()
.when(inpredicate,qtyexpression.as(Double.class))
.when(outpredicate,builder.neg(qtyexpression).as(Double.class))
.otherwise(0));
return builder.equal(sum.as(Integer.class), 1)
}
从可分页调用它
Page<Stockdiary> page = stockRepository.findAll(spec,pageable);
正在执行以下查询:-
select count(stock0_.stock_id) as col_0_0_ from stock stock0_ cross join session_tbl session_tb1_
where stock0_.session_id=session_tb1_.session_id and
cast(sum(case when stock0_.reason in (?) then stock0_.qty when stock0_.reason in (?) then -stock0_.qty else 101 end) as signed)=1
group by stock0_.reason , stock0_.products_id , session_tb1_.terminal_id
由于 case
语句位于 where
子句之后,我收到 SQL 异常。我不知道为什么 spring 在 where
子句之后放置 case
。
我正在尝试进行动态查询,因为我无法使用静态查询。
最佳答案
本质上,您正在寻求执行 Native Query .
特别是,您可以使用 JPA 功能 SqlResultSetMapping
来定义 native 查询和可保存数据的 DTO 对象之间的映射。
假设满足您需求的 DTO 如下所示:
class ProductQuantity {
private String product;
private Integer quantity;
public ProductQuantity(String product, Integer quantity) {
this.product = product;
this.quantity = quantity;
}
public getProduct() { return this.product; }
public getQuantity() { return this.quantity; }
}
以下定义可以充当 native 查询的映射:
@SqlResultSetMapping(
name = "ProductQuantityMapping",
classes = @ConstructorResult(
targetClass = ProductQuantity.class,
columns = {
@ColumnResult(name = "product", type = String.class),
@ColumnResult(name = "qty", type = Integer.class)
})
)
最后可以调用查询:
Query q = entityManager.createNativeQuery("SELECT Product,SUM(CASE WHEN reason IN ('IN','REFUND') THEN Qty WHEN reason IN ('OUT','WASTE') THEN -Qty ELSE NULL END) AS Qty FROM stock GROUP BY Product");
List<ProductQuantity> result = q.getResultList();
for(ProductQuantity pq : result) {
System.out.println("product: " + pq.getProduct() + ", Quantity: " + pq.getQuantity());
}
有关更多信息/示例,请查看此 article .
关于java - 使用 CriteriaBuilder 的动态查询 JPA 2 规范,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/36699976/