解决Illegal mix of collations (gb2312_chinese_ci,IMPLICIT) and (utf8_general_ci,COERCIBLE) for operati

在sql语句执行之前加上这一句:
set names 'utf8';

这一句话的意思相当于下面的三句指令：
　　SET character_set_client = utf8;
　　SET character_set_results = utf8;
　　SET character_set_connection = utf8;