我是JPA的新手,所以我的问题对于有些人来说可能很简单。
下面是我想转换为JPA的简单SQL查询。我已经有一个名为TimeEnt
的实体类。
SELECT
SUM(TimeEntryActualHours) as UnBilledHrs,
SUM (TimeEntryAmount) as UnbilledAmount
FROM TimeEnt WHERE MatterID = 200
List
的Object
数组(Object[]
)。引用JPA规范中的表述,当在SELECT子句中使用多个select_expressions时,查询结果的类型为Object[]
,其中的元素按照它们在SELECT子句中的指定顺序进行排序,并且与每个select_expressions的结果类型相对应。
换句话说,你在评论中提到的查询类型是被支持的,没有问题。这里是一个代码示例:String qlString = "SELECT AVG(x.price), SUM(x.stocks) FROM Magazine x WHERE ...";
Query q = em.createQuery(qlString);
Object[] results = (Object[]) q.getSingleResult();
for (Object object : results) {
System.out.println(object);
}
假设我们有一个实体称为Product
:
final Query sumQuery = entityManager
.createQuery("SELECT SUM(p.price), SUM(p.sale) FROM Product p WHERE p.item=:ITEM AND ....");
sumQuery.setParameter("ITEM","t1");
final Object result= sumQuery.getSingleResult(); // Return an array Object with 2 elements, 1st is sum(price) and 2nd is sum(sale).
//If you have multiple rows;
final Query sumQuery = entityManager
.createQuery("SELECT SUM(p.price), SUM(p.sale) FROM Product p WHERE p.item in (" + itemlist
+ ") AND ....");
// Return a list of arrays, where each array correspond to 1 item (row) in resultset.
final List<IEniqDBEntity> sumEntityList = sumQuery.getResultList();
EntityManager em = ...
Query q = em.createQuery ("SELECT AVG(x.price) FROM Magazine x");
Number result = (Number) q.getSingleResult ();
敬礼,
Java 持久化查询语言
吧? - ᴠɪɴᴄᴇɴᴛ