Discuz! info: MySQL Query Error

Time: 2021-1-21 5:44am
Script: /bbs/register.php

SQL: SELECT * FROM cdb_settings WHERE variable NOT IN ('bbrules', 'bbrulestxt', 'maxonlines', 'welcomemsg', 'welcomemsgtxt', 'newsletter', 'creditsnotify', 'custombackup')
Error: No database selected
Errno.: 1046

Similar error report has beed dispatched to administrator before.