从数据库加载树

Question

I have some Categories, but some of them have sub-categories. So I have a Tree.

I created a table which called Categories . The id field is the primary key the other field is PARENTID which is foreign key referenced by the id ( To make it hierarchical). you can have a view of data here

I am going to specify a certain id and the query gives me the id 's of that category and all sub-categories . I have red this and this one ,but none of them are not useful.

one more point: I am not asking you to write the query for me. I am just looking for some hints

Answer 1

I'll suggest two options.

1) specify your select to include sub cursors,

select column1, cursor(select * form table2) as cursorOfTable2 from table1

and then in your middle tier code, you can reference the sub cursor, the implementation varies depending on what your middle tier is (j2ee, .net, ...)

2) specify the parent child relationship within your select

select a.id as parentId, b.id as child_id, from table1 a, table2 b
where a.id = b.parentId

And then again in your middle tier code you can create the parent child data structure with this data.

hope that makes sense.