JPQL用选择更新

Question

我正在尝试将本机查询转换为JPQL，但是select的UPDATE存在问题。

UPDATE DocumentBody PP SET PP.prepaidLeft = PP.prepaidLeft + (SELECT R.amount 
FROM ReferencePrepaymentDocument R WHERE PP.documentBodyId = 
R.prepaymentDocumentBodyId AND R.documentHeaderId=:NaglDokRozchID) WHERE EXISTS 
(SELECT R.amount FROM ReferencePrepaymentDocument R WHERE PP.documentBodyId = 
R.prepaymentDocumentBodyId AND R.documentHeaderId=:NaglDokRozchID)

我这样尝试过JOIN：

UPDATE DocumentBody PP SET PP.prepaidLeft = PP.prepaidLeft + amount JOIN 
(select R.amount from ReferencePrepaymentDocument R where PP.documentBodyId = 
R.prepaymentDocumentBodyId and R.documentHeaderId=:NaglDokRozchID) amount ON 
PP.documentBodyId = R.prepaymentDocumentBodyId  where exists (select R.amount 
from ReferencePrepaymentDocument R where PP.documentBodyId = 
R.prepaymentDocumentBodyId and R.documentHeaderId=:NaglDokRozchID)

但是我得到“运算符或期望的位置，得到'JOIN'“。

谢谢。