我有一个树结构，其中每个 Node 有一个父元素，一个 Set< Node>孩子。每个节点都有一个字符串标题，我想在其中选择 Set< String>标题，是该节点和所有父节点的标题。我如何编写这个查询？
单个标题的查询就是这样，但就像我说的，我希望它扩展到整个家长分支。 / p>
SELECT node.title FROM节点WHERE node.id =：id干杯
Nik
解决方案你不能用HQL进行递归查询。 查看此。如前所述，它甚至没有标准的SQL。您有两种选择： make多个查询。例如：
<我肯定会选择第二种方式。
I have a tree structure where each Node has a parent and a Set<Node> children. Each Node has a String title, and I want to make a query where I select Set<String> titles, being the title of this node and of all parent nodes. How do I write this query?
The query for a single title is this, but like I said, I'd like it expanded for the entire branch of parents.
SELECT node.title FROM Node node WHERE node.id = :idCheers
Nik
解决方案You can't do recursive queries with HQL. See this. And as stated there it is not even standard SQL. You have two options:
- write a vendor-specific recursive native SQL query
make multiple queries. For example:
// obtain the first node using your query while (currentNode.parent != null) { Query q = //create the query q.setParameter("id", currentNode.getParentId()); Node currentNode = (Node) q.getSingleResult(); nodes.add(currentNode); // this is the Set }
I'd definitely go for the 2nd option.
更多推荐
HQL递归,我该怎么做？
发布评论