if
  test -f my_file
then
  echo 'hi'
  echo 'EXISTS'
else
  echo 'NOT EXISTS'
fi

if [[ "$1" = "" || "$2" = "" ]]
then
  echo Usage :
  echo ' export_query.sh WORK_DIR LAST_CHECK_DATE'
  echo Ex :
  echo ' export_query.sh /data/src_changed 20090810'
  exit -1
fi