code: private String toSQLClause(FieldCriteria c, ClassDescriptor cld)
      {
          String colName = toSqlClause(c.getAttribute(), cld);
          return colName + c.getClause() + c.getValue();
      }
docs: Answer the SQL-Clause for a FieldCriteria
  
  @param c FieldCriteria
  @param cld ClassDescriptor