jpa @query 不认识IFNULL的解决办法

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心血来潮想学习下jpa，然后我就发现我已经站在凉了的边缘：各种坑爹的语法让我生不如死！！！！

比如我一个简单的查询：需求是查询业务员的佣金，sql语句如下：

一点问题没有；

然后转换成jpa语法：

   @Query(value = "select new map(t.orderNum,(select m.username from MembersPO m where" +
                " m.id = t.member_id)as username,\n" +
                " t.sumFinalPrice, IFNULL((select item.benfit from ItemPO item where " +
                "item.id = mi.item_id)*sum(mi.buyFinalPrice),0) \n" +
                "\tas\tcommission ,t.createTime as createTime)\n" +
                " from PurchaseOrderPO t , PurchaseOrderItemPO mi \n" +
                " where mi.purchaseOrderId = t.id\n" +
                "\n" +
                " and t.sendStatus = 1\n" +
                "\tGROUP BY mi.purchaseOrderId \n" +
                "\n" +
                " order by t.id desc ",
                countQuery = "select count(t.orderNum) from PurchaseOrderPO t, PurchaseOrderItemPO mi "  +
                " where mi.purchaseOrderId = t.id\n" +
                        " and t.sendStatus = 1\n" +
                        "\tGROUP BY mi.purchaseOrderId \n"

然后悲剧来了：

各种百度，找不到答案，谷歌一把，在https://stackoverflow.com/questions/27329843/how-to-use-isnull-in-jpa

找到答案了

改完后程序启动正常！