SqlHelper::getDatetimeToDateFunction

public function getDatetimeToDateFunction($value);

/**
 * Returns database expression for converting $field value according the $format.
 * 

 * Following format parts converted:
 * - YYYY   A full numeric representation of a year, 4 digits
 * - MMMM   A full textual representation of a month, such as January or March
 * - MM     Numeric representation of a month, with leading zeros
 * - MI     Minutes with leading zeros
 * - M      A short textual representation of a month, three letters
 * - DD     Day of the month, 2 digits with leading zeros
 * - HH     24-hour format of an hour with leading zeros
 * - H      24-hour format of an hour without leading zeros
 * - GG     12-hour format of an hour with leading zeros
 * - G      12-hour format of an hour without leading zeros
 * - SS     Seconds with leading zeros
 * - TT     AM or PM
 * - T      AM or PM
 * 

 * $field parameter is SQL unsafe.
 *
 * @param string $format Format string.
 * @param string $field Database field or expression.
 *
 * @return string
 */
abstract public function formatDate($format, $field = null);

/**
 * Returns function for getting part of string.
 * 

 * If length is null or omitted, the substring starting
 * from start until the end of the string will be returned.
 * 

 * $str and $from parameters are SQL unsafe.
 *
 * @param string $str Database field or expression.
 * @param integer $from Start position.
 * @param integer $length Maximum length.
 *
 * @return string
 */
public function getSubstrFunction($str, $from, $length = null)
{
	$sql = 'SUBSTR('.$str.', '.$from;

	if (!is_null($length))
		$sql .= ', '.$length;

	return $sql.')';
}