现有表:
ID FdateTime Empid Balance342 2008-01-02 11:57:07.000 7943 96.50
1635 2008-01-03 11:31:41.000 7943 93.00
2453 2008-01-03 17:59:42.000 7943 89.50
3047 2008-01-04 11:37:03.000 7943 86.00
3502 2008-01-04 17:17:32.000 7943 82.50
56 2008-01-02 11:30:52.000 7947 96.50
58 2008-01-02 12:30:52.000 7947 93.00
1633 2008-01-03 11:31:34.000 7947 90.50
2996 2008-01-04 11:30:04.000 7947 89.50
51 2008-01-02 11:22:45.000 7948 96.50
2056 2008-01-03 12:05:08.000 7948 93.00
2984 2008-01-04 11:23:45.000 7948 89.50
3084 2008-01-04 17:23:45.000 7948 76.00求一条SQL语句得出每天最大的ID所对应的值,结果如下:ID FdateTime Empid Balance342 2008-01-02 11:57:07.000 7943 96.50
2453 2008-01-03 17:59:42.000 7943 89.50
3502 2008-01-04 17:17:32.000 7943 82.50
58 2008-01-02 12:30:52.000 7947 93.00
1633 2008-01-03 11:31:34.000 7947 90.50
2996 2008-01-04 11:30:04.000 7947 89.50
51 2008-01-02 11:22:45.000 7948 96.50
2056 2008-01-03 12:05:08.000 7948 93.00
3084 2008-01-04 17:23:45.000 7948 76.00
ID FdateTime Empid Balance342 2008-01-02 11:57:07.000 7943 96.50
1635 2008-01-03 11:31:41.000 7943 93.00
2453 2008-01-03 17:59:42.000 7943 89.50
3047 2008-01-04 11:37:03.000 7943 86.00
3502 2008-01-04 17:17:32.000 7943 82.50
56 2008-01-02 11:30:52.000 7947 96.50
58 2008-01-02 12:30:52.000 7947 93.00
1633 2008-01-03 11:31:34.000 7947 90.50
2996 2008-01-04 11:30:04.000 7947 89.50
51 2008-01-02 11:22:45.000 7948 96.50
2056 2008-01-03 12:05:08.000 7948 93.00
2984 2008-01-04 11:23:45.000 7948 89.50
3084 2008-01-04 17:23:45.000 7948 76.00求一条SQL语句得出每天最大的ID所对应的值,结果如下:ID FdateTime Empid Balance342 2008-01-02 11:57:07.000 7943 96.50
2453 2008-01-03 17:59:42.000 7943 89.50
3502 2008-01-04 17:17:32.000 7943 82.50
58 2008-01-02 12:30:52.000 7947 93.00
1633 2008-01-03 11:31:34.000 7947 90.50
2996 2008-01-04 11:30:04.000 7947 89.50
51 2008-01-02 11:22:45.000 7948 96.50
2056 2008-01-03 12:05:08.000 7948 93.00
3084 2008-01-04 17:23:45.000 7948 76.00
(爱新觉罗.毓华 2007-10-23于浙江杭州)
/*
数据如下:
name val memo
a 2 a2(a的第二个值)
a 1 a1--a的第一个值
a 3 a3:a的第三个值
b 1 b1--b的第一个值
b 3 b3:b的第三个值
b 2 b2b2b2b2
b 4 b4b4
b 5 b5b5b5b5b5
*/
--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
/*
name val memo
---------- ----------- --------------------
a 3 a3:a的第三个值
b 5 b5b5b5b5b5
*/--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
/*
name val memo
---------- ----------- --------------------
a 1 a1--a的第一个值
b 1 b1--b的第一个值
*/--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
/*
name val memo
---------- ----------- --------------------
a 2 a2(a的第二个值)
b 1 b1--b的第一个值
*/--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
/*
name val memo
---------- ----------- --------------------
a 1 a1--a的第一个值
b 5 b5b5b5b5b5
*/--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
/*
name val memo
---------- ----------- --------------------
a 1 a1--a的第一个值
a 2 a2(a的第二个值)
b 1 b1--b的第一个值
b 2 b2b2b2b2
*/--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
/*
name val memo
---------- ----------- --------------------
a 2 a2(a的第二个值)
a 3 a3:a的第三个值
b 4 b4b4
b 5 b5b5b5b5b5
*/
--七,如果整行数据有重复,所有的列都相同。
/*
数据如下:
name val memo
a 2 a2(a的第二个值)
a 1 a1--a的第一个值
a 1 a1--a的第一个值
a 3 a3:a的第三个值
a 3 a3:a的第三个值
b 1 b1--b的第一个值
b 3 b3:b的第三个值
b 2 b2b2b2b2
b 4 b4b4
b 5 b5b5b5b5b5
*/
--在sql server 2000中只能用一个临时表来解决,生成一个自增列,先对val取最大或最小,然后再通过自增列来取数据。
--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', 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('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')
goselect * , px = identity(int,1,1) into tmp from tbselect m.name,m.val,m.memo from
(
select t.* from tmp t where val = (select min(val) from tmp where name = t.name)
) m where px = (select min(px) from
(
select t.* from tmp t where val = (select min(val) from tmp where name = t.name)
) n where n.name = m.name)drop table tb,tmp/*
name val memo
---------- ----------- --------------------
a 1 a1--a的第一个值
b 1 b1--b的第一个值(2 行受影响)
*/
--在sql server 2005中可以使用row_number函数,不需要使用临时表。
--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', 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('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')
goselect m.name,m.val,m.memo from
(
select * , px = row_number() over(order by name , val) from tb
) m where px = (select min(px) from
(
select * , px = row_number() over(order by name , val) from tb
) n where n.name = m.name)drop table tb/*
name val memo
---------- ----------- --------------------
a 1 a1--a的第一个值
b 1 b1--b的第一个值(2 行受影响)
*/
insert into tb values(342 ,'2008-01-02 11:57:07.000', 7943, 96.50)
insert into tb values(1635 ,'2008-01-03 11:31:41.000', 7943, 93.00)
insert into tb values(2453 ,'2008-01-03 17:59:42.000', 7943, 89.50)
insert into tb values(3047 ,'2008-01-04 11:37:03.000', 7943, 86.00)
insert into tb values(3502 ,'2008-01-04 17:17:32.000', 7943, 82.50)
insert into tb values(56 ,'2008-01-02 11:30:52.000', 7947, 96.50)
insert into tb values(58 ,'2008-01-02 12:30:52.000', 7947, 93.00)
insert into tb values(1633 ,'2008-01-03 11:31:34.000', 7947, 90.50)
insert into tb values(2996 ,'2008-01-04 11:30:04.000', 7947, 89.50)
insert into tb values(51 ,'2008-01-02 11:22:45.000', 7948, 96.50)
insert into tb values(2056 ,'2008-01-03 12:05:08.000', 7948, 93.00)
insert into tb values(2984 ,'2008-01-04 11:23:45.000', 7948, 89.50)
insert into tb values(3084 ,'2008-01-04 17:23:45.000', 7948, 76.00)
goselect t.* from tb t where id = (select max(id) from tb where convert(varchar(10),fdatetime,120) = convert(varchar(10),t.fdatetime,120))drop table tb/*
ID FdateTime Empid Balance
----------- ------------------------------------------------------ ----------- --------------------
342 2008-01-02 11:57:07.000 7943 96.50
2453 2008-01-03 17:59:42.000 7943 89.50
3502 2008-01-04 17:17:32.000 7943 82.50(所影响的行数为 3 行)
*/
SELECT a.* FROM a
INNER JOIN
(SELECT MAX(id) md,CONVERT(VARCHAR(10),FdateTime,120) myDate GROUP BY CONVERT(VARCHAR(10),FdateTime,120)) b
ON CONVERT(VARCHAR(10),FdateTime,120) = myDate AND md=ID如果id没有重复值,那么语句简化为
--SELECT a.* FROM a
INNER JOIN
(SELECT MAX(id) md GROUP BY CONVERT(VARCHAR(10),FdateTime,120)) b
ON md=ID--或者可以用SELECT a.* FROM a
WHERE ID IN
(SELECT MAX(id) md GROUP BY CONVERT(VARCHAR(10),FdateTime,120))
INNER JOIN
(SELECT MAX(id) md,CONVERT(VARCHAR(10),FdateTime,120) myDate GROUP BY CONVERT(VARCHAR(10),FdateTime,120)) b
ON CONVERT(VARCHAR(10),FdateTime,120) = myDate AND md=ID--如果id没有重复值,那么语句简化为
SELECT a.* FROM a
INNER JOIN
(SELECT MAX(id) md GROUP BY CONVERT(VARCHAR(10),FdateTime,120)) b
ON md=ID--或者可以用SELECT a.* FROM a
WHERE ID IN
(SELECT MAX(id) md GROUP BY CONVERT(VARCHAR(10),FdateTime,120))
INNER JOIN
(SELECT MAX(id) md,CONVERT(VARCHAR(10),FdateTime,120) myDate FROM tb GROUP BY CONVERT(VARCHAR(10),FdateTime,120)) b
ON CONVERT(VARCHAR(10),FdateTime,120) = myDate AND md=ID--如果id没有重复值,那么语句简化为
SELECT a.* FROM tb a
INNER JOIN
(SELECT MAX(id) md FROM tb GROUP BY CONVERT(VARCHAR(10),FdateTime,120)) b
ON md=ID--或者可以用SELECT a.* FROM a
WHERE ID IN
(SELECT MAX(id) md FROM tb GROUP BY CONVERT(VARCHAR(10),FdateTime,120))