Discuz! info: MySQL Query Error

Time: 2017-12-16 10:45am
Script:

SQL: SELECT t.tid, t.subject, f.name FROM cdb_threads t LEFT JOIN cdb_forums f ON f.fid=t.fid WHERE t.fid='59' ORDER BY t.lastpost DESC LIMIT 10
Error: No database selected
Errno.: 1046

Similar error report has beed dispatched to administrator before.