1,某条数据放首位，其他倒序并分页
select * from student order by(
case
when id='2' then 1
ELSE 4
END),id desc limit 0,5;
2,给查询的每条记录添加编号
select (@i:=@i+1) no , s.* from student s , (select @i:=0) as i
3,数据存在则修改，不存在则添加
replace into student(id,name,age,sex) values(
select s.id from student s where s.name='张三' limit 1),'张三','18'，‘男’);
4,创建副表，并备份表数据
DROP TABLE IF EXISTS 'student_bak';
create table student_bak like student;
insert into student_bak select * from student;
5,根据t表的时间，实现左右表的全连接，并格式化时间，空数据替换
select t.ID,t.TRANSACT_TIME,ifnull(T1.RMB_MONRY,'0.00'),ifnull(T1.RMB_NUM,'0'),ifnull(T2.MY_MONRY,'0.00'),ifnull(T2.MY_NUM,'0') from(
select (@i:=@i+1) ID,DATE_FROMAT(tansact_time,'%Y-%m-%d')TRANSACT_TIME from bank_stages_transact,(select @i:=0) as i
where status = '0' group by DATE_FROMAT(transact_time,'%Y-%m-%d') desc) t
left join
(select DATE_FROMAT(tansact_time,'%Y-%m-%d')TRANSACT_TIME,SUM(transact_monry)RMB_MONEY,COUNT(1)RMB_NUM from bank_stages_transact
where status = '0' and currency_name = '人民币' group by DATE_FROMAT(transact_time,'%Y-%m-%d') desc) t1
on t.transact_time = t1.transact_time
left join
(select DATE_FROMAT(tansact_time,'%Y-%m-%d')TRANSACT_TIME,SUM(transact_monry)MY_MONEY,COUNT(1)MY_NUM from bank_stages_transact
where status = '0' and currency_name = '美元' group by DATE_FROMAT(transact_time,'%Y-%m-%d') desc) t2
on t.transact_time = t2.transact_time
)
6,统计不同年龄的总人数及男女生各有多少人
select age,GROUP_CONCAT(sex)sex,count(1) from student group by age desc