报错信息：
1267- Illegal mix of collations (utf8_unicode_ci,IMPLICIT) and (utf8_general_ci,IMPLICIT) for operation '=
问题描述：
SELECT distinct a.user_id INTO userID FROM authorization_record a WHERE a.open_id = openId AND a.auth_type = '5001';
错误如下：
[Err]1267- Illegal mixofcollations (utf8_unicode_ci,IMPLICIT)and(utf8_general_ci,IMPLICIT)foroperation'='
解决方法：
将比较等式一边进行字符串转换，如改为“CONVERT(b.fullCode USING utf8) COLLATE utf8_unicode_ci”
SELECT distinct a.user_id INTO userID FROM authorization_record a WHERE a.open_id = CONVERT(openId USING utf8) COLLATE utf8_unicode_ci AND a.auth_type = '5001';
