1. 首先需要新建首字母字段rs_first
2. 执行下面语句，更新首字母到rs_first
UPDATE biao
INNER JOIN(
Select rd_id,rs_name ,
ELT(INTERVAL(CONV(HEX(left(CONVERT(rs_name USING gbk),1)),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') as rs_first
FROM biao) tl
ON tl.rd_id = rec_recruit_data_2029.rd_id
set biao.rs_first = tl.rs_first;
