iamwiam的博客

1. 慢查询语句及执行计划EXPLAINSELECT COUNT(id)FROM tb_record_topics_feedbackWHERE is_effective = 1AND ( ( phase_code = '03' AND subject_code = '02' ) OR ( phase_code = '04' AND subject_code = '02' ) OR ( phase_code = '05' AND subject_code =

插入语句：insert into person(id,name,age,sex)values(1,’黄蓉’,24,’女’); 报错：Incorrect string value: ‘\xBB\xC6\xC8\xD8’ for column ‘name’ at row 1 分析：这是中文乱码的原因，深层原因是UTF-8编码有可能是两个、三个、四个字节。Emoji表情或者某些特殊字符是4个字节，

1.题目描述查找最晚入职员工的所有信息 create table employee( emp_no int(11) not null, birth_date date not null, first_name varchar(14) not null, last_name varchar(16) not null, gender char(1) not null, hire_date

1.题目描述 查找入职员工时间排名倒数第三的员工所有信息 create table employees (emp_no int(11) not null, birth_date date not null, first_name varchar(14) not null, last_name varchar(16) not null, gender char(1) not null,