code: public static String getKeysWhereSQL(Class<?> clazz) 
  			throws NoKeyColumnAnnotationException {
  		List<Field> keyFields = DOInfoReader.getKeyColumns(clazz);
  		String where = joinWhere(keyFields, "AND");
  		return autoSetSoftDeleted("WHERE " + where, clazz);
  	}
docs: 获得主键where子句，包含where关键字。会自动处理软删除条件
  
  @param clazz
  @throws NoKeyColumnAnnotationException