how to resolve this symfony error :
C:\inetpub\wwwroot\project\trunk\preprod\signup>php symfony doctrine:build-schema --trace
>> doctrine generating yaml schema from database
[sfException]
Unknown relation alias table_name
Exception trace:
at C:\inetpub\wwwroot\project\trunk\preprod\signup\lib\vendor\symfony\lib\plugins\sfDoctrinePlugin\lib\cli\sfDoctrineCli.class.php:69
sfDoctrineCli->notifyException at C:\inetpub\wwwroot\ project\trunk\preprod\signup\lib\vendor\symfony\lib\plugins\sfDoctrinePlugin\lib\ven
dor\doctrine\Doctrine\Cli.php:93
Doctrine_Cli->run at C:\inetpub\wwwroot\project\trunk\preprod\signup\lib\vendor\symfony\lib\plugins\sfDoctrinePlugin\lib\task\sfDoctrineB
aseTask.class.php:112
sfDoctrineBaseTask->callDoctrineCli at C:\inetpub\wwwroot\project\trunk\preprod\signup\lib\vendor\symfony\lib\plugins\sfDoctrinePlugin\li
b\task\sfDoctrineBuildSchemaTask.class.php:57
sfDoctrineBuildSchemaTask->execute at C:\inetpub\wwwroot\project\trunk\preprod\signup\lib\vendor\symfony\lib\task\sfBaseTask.class.php:63
sfBaseTask->doRun at C:\inetpub\wwwroot\project\trunk\preprod\signup\lib\vendor\symfony\lib\task\sfTask.class.php:77
sfTask->runFromCLI at C:\inetpub\wwwroot\ project\trunk\preprod\signup\lib\vendor\symfony\lib\command\sfSymfonyCommandApplication.class.ph
p:76
sfSymfonyCommandApplication->run at C:\inetpub\wwwroot\project\trunk\preprod\signup\lib\vendor\symfony\lib\command\cli.php:20
include at C:\inetpub\wwwroot\project\trunk\preprod\signup\symfony:14