letsql="SELECT * FROM `msghistory` WHERE id < :maxId AND ((senderId = :senderId AND targetId = :targetId) OR (targetId = :senderId AND senderId = :targetId)) ORDER BY id DESC LIMIT :pageSize "
letsql="SELECT * FROM `msghistory` WHERE id < :maxId AND ((senderId = :senderId AND targetId = :targetId) OR (targetId = :senderId AND senderId = :targetId)) ORDER BY id DESC LIMIT :pageSize "