MySQL到JPQL内部连接

Question

我刚接触过JPQL，在将我的SQL转换成JPQL方面有些困难。我有一个在MYSQL上工作的简单查询：

SELECT askorder.price, bidorder.price from OrderBook JOIN askorder 
ON OrderBook.ASKORDERID_ORDERID = askorder.ORDERID
JOIN bidorder ON OrderBook.BIDORDERID_ORDERID = bidorder.ORDERID
WHERE askorder.ORDERID = 2;

我曾试图将其翻译成JPQL，但我确信这是错误的。具体来说，我认为这可能是ON关键字，我不知道如何将其转换为JPQL：

@NamedQuery(
    name="findOrderBooksPrices",
    query="SELECT ao.price, bo.price from OrderBook bo, OrderBook ao" +
    "INNER JOIN ao ON bo.ASKORDERID_ORDERID = ao.ORDERID " + 
    "INNER JOIN bo ON OrderBook.BIDORDERID_ORDERID = bo.ORDERID " +
    "WHERE ao.ORDERID = :askOrderId"
)

我得到的错误是：

Internal Exception: Exception [EclipseLink-7158] (Eclipse Persistence
Services - 2.5.0.v20130507-3faac2b): 
org.eclipse.persistence.exceptions.ValidationException
Exception Description: Error encountered when building the @NamedQuery
[findOrderBooksPrices] from entity class [class  
org.eclipse.persistence.internal.jpa.metadata.queries.
NamedQueryMetadata].Internal Exception: java.lang.ClassCastException: 
org.eclipse.persistence.jpa.jpql.parser.NullExpression cannot be cast to 
org.eclipse.persistence.jpa.jpql.parser.IdentificationVariable. Please
see server.log for more details.

我希望它在提交订单id后，从每个订购表中退回价格。

谢谢你找我。干杯，泽布

Answer 1

只是猜测一下：

 query="SELECT ao.price, bo.price FROM OrderBook " +
    "INNER JOIN askorder ao " + 
    "INNER JOIN bidorder bo " +
    "WHERE ao.ORDERID = :askOrderId"