SELECT
	m.id,
	m.nickname,
	m.avatar,
	f.remark,
	//如果remark为空串则取nickname
	( CASE WHEN f.remark = '' THEN m.nickname ELSE f.remark END ) show_name 
FROM
	friend f
	LEFT JOIN member m ON f.friend_id = m.id 
WHERE
	f.member_id = 1 
	AND f.deleted = 0 
ORDER BY
    //按照show_name中文拼音的首字母排序  
	CONVERT ( show_name USING gbk )

判断是否中文

SELECT
	* 
FROM
	friend 
WHERE
	remark REGEXP '[^ -~]'