目前正在重新设计我的Android应用程序以使用ROOM叠加层，非常喜欢它，但遇到了一个我似乎无法解决的问题 .

我的查询：

SELECT 
    s.set_num as setNum, 
    s.name as setName, 
    s.img_url as imgURL, 
    s.theme_id as themeId, 
    t3.full_name as themeFullName,
    (   SELECT COUNT(esl.quantity) as eCount 
        FROM element_set_link_table as esl 
        WHERE esl.set_num = s.set_num 
    ) as elementCount
FROM set_table as s " +
    LEFT OUTER JOIN theme_table as t3 ON s.theme_id = t3.id
    LEFT OUTER JOIN theme_table as t2 ON t3.parent_id = t2.id
    LEFT OUTER JOIN theme_table as t1 ON t2.parent_id = t1.id

Sub Query没有返回任何值，但我知道它有数据，并且从ElementSetLinkDao运行该子查询会产生数据 . MSSQL查询可以为此工作 . 有任何想法吗？

android-room