code: protected void unassignFromUserObjectInDb(final Type _unassignType,
                                                final JAASSystem _jaasSystem,
                                                final AbstractUserObject _object)
          throws EFapsException
      {
          Connection con = null;
          try {
              con = Context.getConnection();
              Statement stmt = null;
              final StringBuilder cmd = new StringBuilder();
              try {
                  cmd.append("delete from ").append(_unassignType.getMainTable().getSqlTable()).append(" ").append(
                                  "where USERJAASSYSTEM=").append(_jaasSystem.getId()).append(" ").append(
                                  "and USERABSTRACTFROM=").append(getId()).append(" ").append("and USERABSTRACTTO=")
                                  .append(_object.getId());
  
                  stmt = con.createStatement();
                  stmt.executeUpdate(cmd.toString());
  
              } catch (final SQLException e) {
                  AbstractUserObject.LOG.error("could not execute '" + cmd.toString()
                          + "' to unassign user object '" + toString()
                          + "' from object '" + _object + "' for JAAS system '" + _jaasSystem + "' ", e);
                  throw new EFapsException(getClass(), "unassignFromUserObjectInDb.SQLException", e, cmd.toString(),
                                  getName());
              } finally {
                  try {
                      if (stmt != null) {
                          stmt.close();
                      }
                      con.commit();
                  } catch (final SQLException e) {
                      AbstractUserObject.LOG.error("Could not close a statement.", e);
                  }
              }
          } finally {
              try {
                  if (con != null && !con.isClosed()) {
                      con.close();
                  }
              } catch (final SQLException e) {
                  throw new CacheReloadException("Cannot read a type for an attribute.", e);
              }
          }
      }
docs: Unassign this user object from the given user object for given JAAS
  system.
  
  @param _unassignType type used to unassign (in other words the
  relationship type)
  @param _jaasSystem JAAS system for which this user object is unassigned
  from given object
  @param _object user object from which this user object is unassigned
  @throws EFapsException if unassignment could not be done