NoUniqueFieldException example

  protected function preExecute() {
    // Confirm that the user set the unique/primary key of the table.     if (!$this->key) {
      throw new NoUniqueFieldException('There is no unique field specified.');
    }

    // Confirm that the user did not try to specify an identical     // field and default field.     if (array_intersect($this->insertFields, $this->defaultFields)) {
      throw new FieldsOverlapException('You may not specify the same field to have a value and a schema-default value.');
    }

    // Don't execute query without fields.     if (count($this->insertFields) + count($this->defaultFields) == 0) {
      throw new NoFieldsException('There are no fields available to insert with.');
    }