MySQL取姓名的首字母

set @name='张三';

select
@name,
char_length(@name),
case when char_length(@name)=1 then
         ELT(
         INTERVAL(
           CONV(HEX(CONVERT(substr(@name,1,1) USING GBK)),16,10),
         	0xB0A1,0xB0C5,0xB2C1,0xB4EE,0xB6EA,0xB7A2,0xB8C1,0xB9FE,0xBBF7,0xBFA6,0xC0AC
         ,0xC2E8,0xC4C3,0xC5B6,0xC5BE,0xC6DA,0xC8BB,0xC8F6,0xCBFA,0xCDDA ,0xCEF4,0xD1B9,0xD4D1),
         'A','B','C','D','E','F','G','H','J','K','L','M','N','O','P','Q','R','S','T','W','X','Y','Z')
		 when char_length(@name)=2 then
		     concat(
		     ELT(
         INTERVAL(
           CONV(HEX(CONVERT(substr(@name,1,1) USING GBK)),16,10),
         	0xB0A1,0xB0C5,0xB2C1,0xB4EE,0xB6EA,0xB7A2,0xB8C1,0xB9FE,0xBBF7,0xBFA6,0xC0AC
         ,0xC2E8,0xC4C3,0xC5B6,0xC5BE,0xC6DA,0xC8BB,0xC8F6,0xCBFA,0xCDDA ,0xCEF4,0xD1B9,0xD4D1),
         'A','B','C','D','E','F','G','H','J','K','L','M','N','O','P','Q','R','S','T','W','X','Y','Z'),
				 ELT(
         INTERVAL(
           CONV(HEX(CONVERT(substr(@name,2,1) USING GBK)),16,10),
         	0xB0A1,0xB0C5,0xB2C1,0xB4EE,0xB6EA,0xB7A2,0xB8C1,0xB9FE,0xBBF7,0xBFA6,0xC0AC
         ,0xC2E8,0xC4C3,0xC5B6,0xC5BE,0xC6DA,0xC8BB,0xC8F6,0xCBFA,0xCDDA ,0xCEF4,0xD1B9,0xD4D1),
         'A','B','C','D','E','F','G','H','J','K','L','M','N','O','P','Q','R','S','T','W','X','Y','Z'))
     end