protected function get_sql_for_clause( $query, $parent_query ) {
		global $wpdb;

		// The sub-parts of a $where part.
		$where_parts = array();

		$column = ( ! empty( $query['column'] ) ) ? esc_sql( $query['column'] ) : $this->column;

		$column = $this->validate_column( $column );

		$compare = $this->get_compare( $query );

		$inclusive = ! empty( $query['inclusive'] );

		// Assign greater- and less-than values.
		$lt = '<';
		$gt = '>';

		if ( $inclusive ) {
			$lt .= '=';
			$gt .= '=';
		}

		// Range queries.
		if ( ! empty( $query['after'] ) ) {
			$where_parts[] = $wpdb->prepare( "$column $gt %s", $this->build_mysql_datetime( $query['after'], ! $inclusive ) );
		}
		if ( ! empty( $query['before'] ) ) {
			$where_parts[] = $wpdb->prepare( "$column $lt %s", $this->build_mysql_datetime( $query['before'], $inclusive ) );
		}
		// Specific value queries.

		if ( isset( $query['year'] ) && $value = $this->build_value( $compare, $query['year'] ) )
			$where_parts[] = "YEAR( $column ) $compare $value";

		if ( isset( $query['month'] ) && $value = $this->build_value( $compare, $query['month'] ) ) {
			$where_parts[] = "MONTH( $column ) $compare $value";
		} elseif ( isset( $query['monthnum'] ) && $value = $this->build_value( $compare, $query['monthnum'] ) ) {
			$where_parts[] = "MONTH( $column ) $compare $value";
		}
		if ( isset( $query['week'] ) && false !== ( $value = $this->build_value( $compare, $query['week'] ) ) ) {
			$where_parts[] = _wp_mysql_week( $column ) . " $compare $value";
		} elseif ( isset( $query['w'] ) && false !== ( $value = $this->build_value( $compare, $query['w'] ) ) ) {
			$where_parts[] = _wp_mysql_week( $column ) . " $compare $value";
		}
		if ( isset( $query['dayofyear'] ) && $value = $this->build_value( $compare, $query['dayofyear'] ) )
			$where_parts[] = "DAYOFYEAR( $column ) $compare $value";

		if ( isset( $query['day'] ) && $value = $this->build_value( $compare, $query['day'] ) )
			$where_parts[] = "DAYOFMONTH( $column ) $compare $value";

		if ( isset( $query['dayofweek'] ) && $value = $this->build_value( $compare, $query['dayofweek'] ) )
			$where_parts[] = "DAYOFWEEK( $column ) $compare $value";

		if ( isset( $query['dayofweek_iso'] ) && $value = $this->build_value( $compare, $query['dayofweek_iso'] ) )
			$where_parts[] = "WEEKDAY( $column ) + 1 $compare $value";

		if ( isset( $query['hour'] ) || isset( $query['minute'] ) || isset( $query['second'] ) ) {
			// Avoid notices.
			foreach ( array( 'hour', 'minute', 'second' ) as $unit ) {
				if ( ! isset( $query[ $unit ] ) ) {
					$query[ $unit ] = null;
				}
			}

			if ( $time_query = $this->build_time_query( $column, $compare, $query['hour'], $query['minute'], $query['second'] ) ) {
				$where_parts[] = $time_query;
			}
		}

		/*
		 * Return an array of 'join' and 'where' for compatibility
		 * with other query classes.
		 */
		return array(
			'where' => $where_parts,
			'join'  => array(),
		);
	}