Need to call up custom field in "lastpostby" template from thread table

[omardealo]

ok , i try this code and the hook : cache_ordered_forums
Shows me this error

PHP Code:

Database error in vBulletin 3.8.7:

Invalid SQL:

                SELECT forum.forumid, lastpost, lastposter, lastthread, lastthreadid, lasticonid, threadcount, replycount, lastpostid, lastprefixid, thread.threadphoto
                    
                FROM forum AS forum
                
                 LEFT JOIN thread AS thread ON (thread.threadid = forum.lastthreadid);

MySQL Error   : Column 'lastpost' in field list is ambiguous
Error Number  : 1052
Request Date  : Friday, February 8th 2013 @ 06:58:38 PM
Error Date    : Friday, February 8th 2013 @ 06:58:38 PM
Script        : http://localhost/386/index.php
Referrer      : http://localhost/386/showthread.php?p=71
IP Address    : 127.0.0.1
Username      : admin
Classname     : vB_Database
MySQL Version : 5.0.51b-community-nt-log 


Note : some forum on lastthreadid filed = 0