主要按照日期獲得最新的數(shù)據(jù)；

今天記錄兩種方式，并不涉及效率等其他方面問題：

第一種， 利用GROUP BY原理：

select * from (

select * from `authenticationrecord` order by `authenticationtime` desc

) `temp` group by merchantrid order by `authenticationtime` desc

第二種，利用mysql內(nèi)置函數(shù)

select * from `test` where id in(select SUBSTRING_INDEX(group_concat(id order by `date` desc),',',1) from `test` group by category_id ) order by `date` desc

<<<<<<<><>

試驗?zāi)_本(自己玩)：

create table STAFF(

id int,

sname varchar(50),

dept varchar(50),

salary int,

edlevel int,

hiredate datetime

)

insert into STAFF values('1','張三','開發(fā)部','2000','3','2009-10-11');

insert into STAFF values('2','李四','開發(fā)部','2500','3','2009-10-01');

insert into STAFF values('3','王五','設(shè)計部','2600','5','2010-10-02');

insert into STAFF values('4','王六','設(shè)計部','2300','4','2010-10-03');

insert into STAFF values('5','馬七','設(shè)計部','2100','4','2010-10-06');

insert into STAFF values('6','趙八','銷售部','3000','5','2010-10-05');

insert into STAFF values('7','錢九','銷售部','3100','7','2010-10-07');

insert into STAFF values('8','孫十','銷售部','3500','7','2010-10-06');

select group_concat(id order by hiredate desc) as test from staff

group by dept;

select * from STAFF;

select * from STAFF

group by dept

參考網(wǎng)站：http://blog.csdn.net/agileclipse/article/details/12184635

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