带有SELECT问题的SQL UPDATE。 SQL语法错误

Question

我的SQL有问题。我想使用select来进行更新，但到目前为止我还没能完成它。如果有人能帮助我，我真的会感到沮丧。我是MySQL的新手。有问题的查询是：

UPDATE
    pac
SET 
    pac.pac_spc_id = dtn_atual.spc_id
FROM 
    pac_paciente pac
INNER JOIN (    SELECT 
                    dtn.dtn_pac_id,
                    spc_id
                FROM  `pac_destino` dtn
                INNER JOIN ( select 
                                 des.dtn_pac_id, 
                                 MAX(CONCAT(des.dtn_data, des.dtn_seq)) AS datamax  
                            FROM pac_destino des
                            GROUP BY des.`dtn_pac_id`
                           ) AS d1 ON d1.dtn_pac_id = dtn.dtn_pac_id
                        AND d1.datamax = CONCAT(dtn.dtn_data, dtn.dtn_seq)
                LEFT JOIN pac_classdestino c1 ON c1.cdo_id = dtn.dtn_cdo_id
                LEFT JOIN pac_statuspaciente spc ON spc.spc_id = c1.cdo_spc_id
                ) AS dtn_atual on dtn_atual.dtn_pac_id = pac.`pac_id`

生成的错误是

You have an error in your SQL syntax; check the manual that 
corresponds to your MySQL server version for the right syntax 
to use near 'FROM pac_paciente pac INNER JOIN (    SELECT  
   dtn.dtn_pac_id, spc_id
   ' at line 5