如何使用HQL与查找函数Grails(Gorm)使用SELECT

Question

我是Grails的新手，并通过其文档在线学习。

一件事使我在阅读有关（）函数时都感到困惑。

Book.find(String query) // pass the HQL, However there are various overloaded variants.

现在，如果我使用此find()函数。

Category.find("from Category as cat where cat.id = ? ", [5L]) //result is fine.

我的类别类

class Category {
    String title;
    String description
    String image
    static constraints = {
        title blank: false, nullable: false
        description blank: true, nullable: true
    }
}

，但是如果我尝试了此HQL查询

 Category.find("select  cat.description from Category as cat where cat.id = ? ", [5L])
//or this query.
 Category.find("select description from Category as cat where cat.id = ? ", [5L])

它引起了例外： -

Invalid query [select  cat.description from Category as cat where cat.id = ? ] for domain class [class com.ecommerce.domain.Category]. Stacktrace follows:
Message: Invalid query [select  cat.description from Category as cat where cat.id = ? ] for domain class [class com.ecommerce.domain.Category]

所以，如果我的HQL有任何问题，请评论.....

或您可以回答如何使用find(String query) ??

Answer 1

对于单个结果：

Category.find("from Category cat where cat.id = ?", [5L])?.description

或倍数：

Category.find("from Category cat where cat.id = ?", [5L]).collect{ it.description }