[英]JPA Select Count Distinct
I need a relatively simple query, but JPA makes it kind of hard to create it. 我需要一个相对简单的查询,但是JPA使其很难创建。
The SQL variant would look like this: SQL变量如下所示:
SELECT COUNT(DISTINCT OrderID) AS DistinctOrders FROM Orders WHERE CustomerID=7;
[Edit: OrderID is NOT the primary key. [编辑:OrderID不是主键。 There can be more OrderId that are equals in the table]
表中可以有更多等于的OrderId]
I need to set the CustomerID
with a variable that is passed to my method. 我需要使用传递给我的方法的变量设置
CustomerID
。
I found documentation on CriteriaQuery
distinct()
but I can't seem to wrap it all together. 我找到了有关
CriteriaQuery
distinct()
文档,但似乎无法将它们全部包装在一起。
This is what I have so far: 这是我到目前为止的内容:
CriteriaBuilder cb = this.em.getCriteriaBuilder();
CriteriaQuery<Order> c = cb.createQuery( Order.class );
Root<Order> order = c.from( Order.class );
Path<String> customerID = order.get( "customerID" );
c.where( cb.equal( customerID, theId ) );
CriteriaBuilder cb = this.em.getCriteriaBuilder();
CriteriaQuery<Long> c = cb.createQuery(Long.class);//the query returns a long, and not Orders
Root<Order> order = c.from( Order.class );
//c.select(cb.countDistinct(order));//and this is the code you were looking for
c.select(cb.countDistinct(order.get("orderID")));//for counting distinct fields other than the primary key
Path<String> customerID = order.get( "customerID" );
c.where( cb.equal( customerID, theId ) );
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.