MongoDB and Sub-query

[cch...@gmail.com]

Hi, I'm having a query with a sub-query which selects the next relevant item of the main query in the same collection but I always get an empty result here

SELECT 

id,

Time AS Time1

(

SELECT

sub.Time

FROM A AS sub

WHERE 

sub.value="Event" AND

sub.Time2 > main.Time1 AND

sub.state BETWEEN 0 AND 2

ORDER BY sub.Time

LIMIT 1

    ) AS Time2

FROM A AS main

WHERE 

    value="Event" AND

    state BETWEEN 3 AND 6

ORDER BY Time1 ASC

The sub-query alone runs perfectly fine. Wondering if there's any constraint running a sub-query or what else could be wrong?