需求是将字符串中的汉字转为拼音。创建一个汉字转拼音的函数，在其中判断每个字符是否为中文，如果是则查询拼音表取得对应的拼音，否则原样返回。网上的大部分 MySQL 转拼音函数都是通过创建一个拼音对照表，然后在自定义函数中查询该表实现的。以下对这种实现做了修改，具有以下特点：
- 不需要拼音表。
- 与数据库字符集无关。
- 根据参数可分别返回全拼小写、全拼大写、全拼首字母大写。
- 不考虑多音字拼音上下文语义的正确性。
- 通过嵌套使用 MySQL 的 elt、interval 函数确定一个汉字对应的唯一拼音。
创建自定义函数
drop function if exists to_pinyin;
delimiter //
create function to_pinyin(name varchar(255) charset gbk, flag int) returns varchar(255) charset gbk
begin
declare mycode int;
declare tmp_lcode varchar(2) charset gbk;
declare lcode int;
declare tmp_rcode varchar(2) charset gbk;
declare rcode int;
declare l_pin_yin_ varchar(6);
declare mypy varchar(255) charset gbk default '';
declare lp int;
set mycode = 0;
set lp = 1;
set name = hex(name);
while lp < length(name) do
set tmp_lcode = substring(name, lp, 2);
set lcode = cast(ascii(unhex(tmp_lcode)) as unsigned);
set tmp_rcode = substring(name, lp + 2, 2);
set rcode = cast(ascii(unhex(tmp_rcode)) as unsigned);
if lcode > 128 then
set mycode =abs(65536 - lcode * 256 - rcode);
-- 取对应的拼音
set l_pin_yin_ = elt(interval(0-mycode,
-20319,-20317,-20304,-20295,-20292,-20283,-20265,-20257,-20242,-20230,-20051,-20036,
-20032,-20026,-20002,-19990,-19986,-19982,-19976,-19805,-19784,-19775,-19774,-19763,
-19756,-19751,-19746,-19741,-19739,-19728,-19725,-19715,-19540,-19531,-19525,-19515,
-19500,-19484,-19479,-19467,-19289,-19288,-19281,-19275,-19270,-19263,-19261,-19249,
-19243,-19242,-19238,-19235,-19227,-19224,-19218,-19212,-19038,-19023,-19018,-19006,
-19003,-18996,-18977,-18961,-18952,-18783,-18774,-18773,-18763,-18756,-18741,-18735,
-18731,-18722,-18710,-18697,-18696,-18526,-18518,-18501,-18490,-18478,-18463,-18448,
-18447,-18446,-18239,-18237,-18231,-18220,-18211,-18201,-18184,-18183,-18181,-18012,
-17997,-17988,-17970,-17964,-17961,-17950,-17947,-17931,-17928,-17922,-17759,-17752,
-17733,-17730,-17721,-17703,-17701,-17697,-17692,-17683,-17676,-17496,-17487,-17482,
-17468,-17454,-17433,-17427,-17417,-17202,-17185,-16983,-16970,-16942,-16915,-16733,
-16708,-16706,-16689,-16664,-16657,-16647,-16474,-16470,-16465,-16459,-16452,-16448,
-16433,-16429,-16427,-16423,-16419,-16412,-16407,-16403,-16401,-16393,-16220,-16216,
-16212,-16205,-16202,-16187,-16180,-16171,-16169,-16158,-16155,-15959,-15958,-15944,
-15933,-15920,-15915,-15903,-15889,-15878,-15707,-15701,-15681,-15667,-15661,-15659,
-15652,-15640,-15631,-15625,-15454,-15448,-15436,-15435,-15419,-15416,-15408,-15394,
-15385,-15377,-15375,-15369,-15363,-15362,-15183,-15180,-15165,-15158,-15153,-15150,
-15149,-15144,-15143,-15141,-15140,-15139,-15128,-15121,-15119,-15117,-15110,-15109,
-14941,-14937,-14933,-14930,-14929,-14928,-14926,-14922,-14921,-14914,-14908,-14902,
-14894,-14889,-14882,-14873,-14871,-14857,-14678,-14674,-14670,-14668,-14663,-14654,
-14645,-14630,-14594,-14429,-14407,-14399,-14384,-14379,-14368,-14355,-14353,-14345,
-14170,-14159,-14151,-14149,-14145,-14140,-14137,-14135,-14125,-14123,-14122,-14112,
-14109,-14099,-14097,-14094,-14092,-14090,-14087,-14083,-13917,-13914,-13910,-13907,
-13906,-13905,-13896,-13894,-13878,-13870,-13859,-13847,-13831,-13658,-13611,-13601,
-13406,-13404,-13400,-13398,-13395,-13391,-13387,-13383,-13367,-13359,-13356,-13343,
-13340,-13329,-13326,-13318,-13147,-13138,-13120,-13107,-13096,-13095,-13091,-13076,
-13068,-13063,-13060,-12888,-12875,-12871,-12860,-12858,-12852,-12849,-12838,-12831,
-12829,-12812,-12802,-12607,-12597,-12594,-12585,-12556,-12359,-12346,-12320,-12300,
-12120,-12099,-12089,-12074,-12067,-12058,-12039,-11867,-11861,-11847,-11831,-11798,
-11781,-11604,-11589,-11536,-11358,-11340,-11339,-11324,-11303,-11097,-11077,-11067,
-11055,-11052,-11045,-11041,-11038,-11024,-11020,-11019,-11018,-11014,-10838,-10832,
-10815,-10800,-10790,-10780,-10764,-10587,-10544,-10533,-10519,-10331,-10329,-10328,
-10322,-10315,-10309,-10307,-10296,-10281,-10274,-10270,-10262,-10260,-10256,-10254),
'a','ai','an','ang','ao','ba','bai','ban','bang','bao','bei','ben',
'beng','bi','bian','biao','bie','bin','bing','bo','bu','ca','cai','can',
'cang','cao','ce','ceng','cha','chai','chan','chang','chao','che','chen','cheng',
'chi','chong','chou','chu','chuai','chuan','chuang','chui','chun','chuo','ci','cong',
'cou','cu','cuan','cui','cun','cuo','da','dai','dan','dang','dao','de',
'deng','di','dian','diao','die','ding','diu','dong','dou','du','duan','dui',
'dun','duo','e','en','er','fa','fan','fang','fei','fen','feng','fo',
'fou','fu','ga','gai','gan','gang','gao','ge','gei','gen','geng','gong',
'gou','gu','gua','guai','guan','guang','gui','gun','guo','ha','hai','han',
'hang','hao','he','hei','hen','heng','hong','hou','hu','hua','huai','huan',
'huang','hui','hun','huo','ji','jia','jian','jiang','jiao','jie','jin','jing',
'jiong','jiu','ju','juan','jue','jun','ka','kai','kan','kang','kao','ke',
'ken','keng','kong','kou','ku','kua','kuai','kuan','kuang','kui','kun','kuo',
'la','lai','lan','lang','lao','le','lei','leng','li','lia','lian','liang',
'liao','lie','lin','ling','liu','long','lou','lu','lv','luan','lue','lun',
'luo','ma','mai','man','mang','mao','me','mei','men','meng','mi','mian',
'miao','mie','min','ming','miu','mo','mou','mu','na','nai','nan','nang',
'nao','ne','nei','nen','neng','ni','nian','niang','niao','nie','nin','ning',
'niu','nong','nu','nv','nuan','nue','nuo','o','ou','pa','pai','pan',
'pang','pao','pei','pen','peng','pi','pian','piao','pie','pin','ping','po',
'pu','qi','qia','qian','qiang','qiao','qie','qin','qing','qiong','qiu','qu',
'quan','que','qun','ran','rang','rao','re','ren','reng','ri','rong','rou',
'ru','ruan','rui','run','ruo','sa','sai','san','sang','sao','se','sen',
'seng','sha','shai','shan','shang','shao','she','shen','sheng','shi','shou','shu',
'shua','shuai','shuan','shuang','shui','shun','shuo','si','song','sou','su','suan',
'sui','sun','suo','ta','tai','tan','tang','tao','te','teng','ti','tian',
'tiao','tie','ting','tong','tou','tu','tuan','tui','tun','tuo','wa','wai',
'wan','wang','wei','wen','weng','wo','wu','xi','xia','xian','xiang','xiao',
'xie','xin','xing','xiong','xiu','xu','xuan','xue','xun','ya','yan','yang',
'yao','ye','yi','yin','ying','yo','yong','you','yu','yuan','yue','yun',
'za','zai','zan','zang','zao','ze','zei','zen','zeng','zha','zhai','zhan',
'zhang','zhao','zhe','zhen','zheng','zhi','zhong','zhou','zhu','zhua','zhuai','zhuan',
'zhuang','zhui','zhun','zhuo','zi','zong','zou','zu','zuan','zui','zun','zuo');
if l_pin_yin_ is null then -- 非汉字取原字符
set mypy = concat(mypy,convert(unhex(substring(name, lp, 4)) using gbk));
else -- 汉字取拼音
set l_pin_yin_ = case flag
when 1 then lower(l_pin_yin_)
when 2 then upper(l_pin_yin_)
when 3 then concat(upper(substr(l_pin_yin_,1,1)),lower(substr(l_pin_yin_,2)))
else lower(l_pin_yin_)
end;
set mypy = concat(mypy,l_pin_yin_);
end if;
set lp = lp + 4;
else -- ASCII字符
set mypy = concat(mypy,char(cast(ascii(unhex(substring(name, lp, 2))) as unsigned)));
set lp = lp + 2;
end if;
end while;
return mypy;
end;
//
delimiter ;
测试
mysql> set @s:='123 中文 ......中a ^华b人 c $民 d共[和]国 Good！';
Query OK, 0 rows affected (0.00 sec)
mysql> select to_pinyin(@s,3);
+----------------------------------------------------------------+
| to_pinyin(@s,3) |
+----------------------------------------------------------------+
| 123 ZhongWen ......Zhonga ^HuabRen c $Min dGong[He]Guo Good！ |
+----------------------------------------------------------------+
1 row in set (0.00 sec)