大家看看这个语句错在哪里,该怎么解决

大家看看这个语句错在哪里
Update   sms_Mo_Port_Log
Set   usertime   =   Trunc(Sysdate-1)   +   (13*60+35)   /(24*60)
From   sms_sendmsg_ago   a,sms_Mo_Port_Log   b
Where   a.msgid_db=b.msgid   And   a.usertime   =   Trunc(Sysdate-1);

报这样的错误:
ORA-00933:   SQL   command   not   properly   ended


------解决方案--------------------
Update sms_Mo_Port_Log b
Set b.usertime = Trunc(Sysdate-1) + (13*60+35) /(24*60)
Where exists (select 'X ' from sms_sendmsg_ago a
where a.msgid_db=b.msgid
And a.usertime = Trunc(Sysdate-1));