สอบถาม MySQL query แล้ว error #1242 - Subquery returns more than 1 row ค่ะ

SELECT DB_table.table_name,DB_time.startSlot
FROM DB_time CROSS JOIN DB_table
WHERE
        (SELECT DB_table.table_name,DB_time.startSlot FROM DB_time CROSS JOIN DB_table) 
NOT IN ( 
    SELECT DB_table.table_name,DB_time.startSlot FROM DB_time CROSS JOIN DB_table LEFT JOIN tspace ON    (DB_time.time_id = tspace.time_id AND DB_table.table_id = tspace.table_id ) WHERE tspace.rdate = '2019-04-07')