Storing and retrieving custom field value of a webform in/from database?

Question

I have altered a webform by adding a date field in different language like chinese in Drupal 7. But what steps are required to store custom field value in database and retrieving value when webform results are accessed?

I used hook_form_alter() to add custom date field in the existing webform, but its value doesn't get stored in database. Do I need to add some extra code to store value of custom field in db?

I am sharing my code.

function tekege_grievanceform_form_alter(&$form, &$form_state, $form_id) { //print_r($form_id);exit;
switch ($form_id) {
    /* for chinese */
    case 'webform_client_form_60224':
        $form['submitted']['dob'] = array(
            '#type' => 'fieldset',
            '#title' => t('出生日期'),
            '#weight' => 4,
            '#prefix' => '<div class="chinese_dob" id="webform_chinese_dob">',
            '#suffix' => '</div>',
            '#required' => 'true'
        );

        $form['submitted']['dob']['dob_month'] = array(
            '#type' => 'select',
            '#default_value' => array('month' => '月'),
            '#options' => array('month' => t('月'),
                1 => t('1 月'), 2 => t('2 月'), 3 => t('3 月'), 4 => t('4 月'), 5 => t('5 月'), 6 => t('6 月'), 7 => t('7 月'), 8 => t('8 月'), 9 => t('9 月'), 10 => t('10 月'), 11 => t('11 月'), 12 => t('12 月'),
            ),
            '#description' => t('Select month.'),
            '#required' => true,
        );

        /* for 31 days */
        $form['submitted']['dob']['dob_day_31'] = array(
            '#type' => 'select',
            '#default_value' => array('day' => '日'),
            '#options' => array('day' => t('日'), 1 => t('1'), 2 => t('2'), 3 => t('3'), 4 => t('4'), 5 => t('5'), 6 => t('6'), 7 => t('7'), 8 => t('8'), 9 => t('9'), 10 => t('10'), 11 => t('11'), 12 => t('12'),
                13 => t('13'), 14 => t('14'), 15 => t('15'), 16 => t('16'), 17 => t('17'), 18 => t('18'), 19 => t('19'), 20 => t('20'), 21 => t('21'), 22 => t('22'), 23 => t('23'), 24 => t('24'),
                25 => t('25'), 26 => t('26'), 27 => t('27'), 28 => t('28'), 29 => t('29'), 30 => t('30'), 31 => t('31')),
            '#description' => t("Thirty-One Days."),
            '#required' => true,
        );

        $form['submitted']['dob']['dob_year'] = array(
            '#type' => 'select',
            '#default_value' => array('year' => '年'),
            '#options' => array('year' => t('年'), 1 => t('2013'), 2 => t('2012'), 3 => t('2011'), 4 => t('2010'), 5 => t('2009'), 6 => t('2008'), 7 => t('2007'), 8 => t('2006'),
                9 => t('2005'), 10 => t('2004'), 11 => t('2003'), 12 => t('2002'), 13 => t('2001'), 14 => t('2000'), 15 => t('1999'), 16 => t('1998'), 17 => t('1997'),
                18 => t('1996'), 19 => t('1995'), 20 => t('1994'), 21 => t('1993'), 22 => t('1992'), 23 => t('1991'), 24 => t('1990'), 25 => t('1989'), 26 => t('1988'),
                27 => t('1987'), 28 => t('1986'), 29 => t('1985'), 30 => t('1984'), 31 => t('1983'), 32 => t('1982'), 33 => t('1981'), 34 => t('1980'), 35 => t('1979'), 36 => t('1978'), 37 => t('1977'), 38 => t('1975'),
                39 => t('1974'), 40 => t('1973'), 41 => t('1972'), 42 => t('1971'), 43 => t('1970'), 44 => t('1969'), 45 => t('1968'), 46 => t('1967'), 47 => t('1966'),
                48 => t('1965'), 49 => t('1964'), 50 => t('1963'), 51 => t('1962'), 52 => t('1961'), 53 => t('1960'), 54 => t('1959'), 55 => t('1958'), 56 => t('1957'),
                57 => t('1956'), 58 => t('1955'), 59 => t('1954'), 60 => t('1953'), 61 => t('1952'), 60 => t('1951'), 61 => t('1950'),
            ),
            '#description' => t('Select year.'),
            '#required' => true,
        );
    }
 }

Answer 1

Solved: I was using devlopment version of webform module that was restricting my custom date fields of webform to get stored in database. It was required to be updated. Anyways thanks for replying.