sql多条记录取最前面一条
有表t1
数据如下:

怎么得到如下数据
如果几条数据有name相同的,就根据time来取最前面一条记录就可以了

这个问题第1个回答：
SQL code

select * from t1 a
where not exists (select 1 from t1 b
   where b.name=a.name
   and b.time>a.time)

这个问题第2个回答：
SQL code

SELECT *
FROM t1 AS t
WHERE NOT EXISTS(
        SELECT *
        FROM t1
        WHERE NAME=t.NAME AND
                [TIME]<[t.TIME]
     )

这个问题第3个回答：
SQL code

按某一字段分组取最大(小)值所在行的数据

(爱新觉罗.毓华 2007-10-23于浙江杭州)

/*

数据如下：

• 创建表并插入数据：

create table tb(name varchar(10),val int,memo varchar(20))
insert into tb values('a',    2,   'a2(a的第二个值)')
insert into tb values('a',    1,   'a1--a的第一个值')
insert into tb values('a',    3,   'a3:a的第三个值')
insert into tb values('b',    1,   'b1--b的第一个值')
insert into tb values('b',    3,   'b3:b的第三个值')
insert into tb values('b',    2,   'b2b2b2b2')
insert into tb values('b',    4,   'b4b4')
insert into tb values('b',    5,   'b5b5b5b5b5')
go

一、按name分组取val最大的值所在行的数据。

• 方法1：

select a.* from tb a where val = (select max(val) from tb where name = a.name) order by a.name

• 方法2：

select a.* from tb a where not exists(select 1 from tb where name = a.name and val > a.val)

• 方法3：

select a.* from tb a,(select name,max(val) val from tb group by name) b where a.name = b.name and a.val = b.val order by a.name

• 方法4：

select a.* from tb a inner join (select name , max(val) val from tb group by name) b on a.name = b.name and a.val = b.val order by a.name

• 方法5

select a.* from tb a where 1 > (select count(*) from tb where name = a.name and val > a.val ) order by a.name

二、按name分组取val最小的值所在行的数据。

• 方法1：

select a.* from tb a where val = (select min(val) from tb where name = a.name) order by a.name

• 方法2：

select a.* from tb a where not exists(select 1 from tb where name = a.name and val < a.val)

• 方法3：

select a.* from tb a,(select name,min(val) val from tb group by name) b where a.name = b.name and a.val = b.val order by a.name

• 方法4：

select a.* from tb a inner join (select name , min(val) val from tb group by name) b on a.name = b.name and a.val = b.val order by a.name

• 方法5

select a.* from tb a where 1 > (select count(*) from tb where name = a.name and val < a.val) order by a.name

三、按name分组取第一次出现的行所在的数据。

select a.* from tb a where val = (select top 1 val from tb where name = a.name) order by a.name

四、按name分组随机取一条数据。

select a.* from tb a where val = (select top 1 val from tb where name = a.name order by newid()) order by a.name

五、按name分组取最小的两个(N个)val

select a.* from tb a where 2 > (select count(*) from tb where name = a.name and val < a.val ) order by a.name,a.val
 
select a.* from tb a where val in (select top 2 val from tb where name=a.name order by val) order by a.name,a.val
 
select a.* from tb a where exists (select count(*) from tb where name = a.name and val < a.val having Count(*) < 2) order by a.name

六、按name分组取最大的两个(N个)val

select a.* from tb a where 2 > (select count(*) from tb where name = a.name and val > a.val ) order by a.name,a.val

select a.* from tb a where val in (select top 2 val from tb where name=a.name order by val desc) order by a.name,a.val

select a.* from tb a where exists (select count(*) from tb where name = a.name and val > a.val having Count(*) < 2) order by a.name

七，如果整行数据有重复，所有的列都相同。

数据如下：