orientdb sql查询选择边和顶点字段属性。

Question

I do have following database structure.

users -> comment -> products

a. users and products are the vertexes that contain some info etc: user_name, product_name and .... b. comment is the edge that contains comment and created/modified date.

what is the sql query may look like in order to show the following result.

Note: i have to show all of the products that may have or no have comment.

1. product_name, user_name, comment, comment_created_date, comment_modified_date
2. product_name, user_name, '', '', ''
3. product_name, user_name, comment, comment_created_date, comment_modified_date

Answer 1

create class User extends V
create property User.name string

create class Product extends V
create property Product.name string

create class Comment extends E
create property Comment.comment string
create property Comment.createDate datetime
create property Comment.modifiedDate datetime


create vertex User set name = 'u1' # 12:0
create vertex Product set name = 'p1' # 13:0
create vertex Product set name = 'p2' # 13:1

create edge Comment from #12:0 to #13:0 set comment = 'nice product', createDate = sysdate()

If the above is your situation, I believe the query you're looking for is something like:

select *, expand(inE('Comment')) from Product

UPDATE:

It's not very pretty, but as a workaround you could use:

select *, inE('Comment').include('comment', 'createDate', 'modifiedDate') from Product

Answer 2

you cannot "join" classes/tables when querying. instead, merge the result sets -> start from the edge class for Product s with Comment s, then use let and unionall() to add the non- Comment ed Product s before expand() ing:

select expand($c)
let $a = (select in.name as name, out.name as User, comment, createDate, modifiedDate from Comment),
    $b = (select from Product where in_Comment is null),
    $c = unionall($a, $b)

note that in the result set you will have the @CLASS field fed with null s from the first query (ie, from the $a result set) and with Product from the second query (the $b result set)

Answer 3

using @vitorenesduarte schema the following query may fit the current requirement

select name AS product_name,in(comment).name 
            AS user_name,inE(comment).comment
            AS comment,inE(comment).createDate
            AS comment_created_date,inE(comment).modifiedDate
            AS comment_modified_date from product