精妙SQL语句,绝对经典
1.说明：复制表(只复制结构,源表名：a新表名：b)
SQL:select *into b from a where 1<>1
2.说明：拷贝表(拷贝数据,源表名：a 目标表名：b)
SQL:insert into b(a,b,c)select
d,e,f from b;
3.说明：显示文章、提交人和最后回复时间
SQL:select
a.title,a.username,b.adddate from table a,(select max(adddate)adddate from
table where table.title=a.title)b
4.说明：外连接查询(表名1：a 表名2：b)
SQL:
select a.a,a.b,a.c,b.c,b.d,b.f from a LEFT OUTER JOIN b ON a.a =b.c
5.说明：日程安排提前五分钟提醒
SQL:select *from 日程安排where
datediff('minute',f开始时间,getdate())>5
6.说明：两张关联表，删除主表中已经在副表中没有的信息
SQL:
delete from info where not exists (select *from infobz
where info.infid=infobz.infid )
说明：--
SQL:
SELECT A.NUM,
A.NAME,B.UPD_DATE,B.PREV_UPD_DATE
FROM TABLE1,
(SELECT X.NUM,
X.UPD_DATE,Y.UPD_DATE PREV_UPD_DATE
FROM (SELECT NUM,UPD_DATE,
INBOUND_QTY,STOCK_ONHAND
FROM TABLE2
WHERE
TO_CHAR(UPD_DATE,'YYYY/MM')=TO_CHAR(SYSDATE,'YYYY/MM'))X,
(SELECT
NUM,UPD_DATE,STOCK_ONHAND
FROM TABLE2
WHERE
TO_CHAR(UPD_DATE,'YYYY/MM')=
TO_CHAR(TO_DATE(TO_CHAR(SYSDATE,
'YYYY/MM')||'/01','YYYY/MM/DD')-1,'YYYY/MM'))Y,
WHERE X.NUM =
Y.NUM （+）
AND X.INBOUND_QTY +NVL(Y.STOCK_ONHAND,0)<>
X.STOCK_ONHAND )B
WHERE A.NUM =B.NUM
说明：--
SQL:
select *from studentinfo where not exists(select *from student where
studentinfo.id=student.id)and 系名称='"&strdepartmentname&"'and
专业名称='"&strprofessionname&"'order by 性别,生源地,高考总成绩
7.说明：
从数据库中去一年的各单位电话费统计(电话费定额贺电化肥清单两个表来源）
SQL:
SELECT
a.userper,a.tel,a.standfee,TO_CHAR(a.telfeedate,'yyyy')AS telyear,
SUM(decode(TO_CHAR(a.telfeedate,'mm'),'01',a.factration))AS JAN,
SUM(decode(TO_CHAR(a.telfeedate,'mm'),'02',a.factration))AS FRI,
SUM(decode(TO_CHAR(a.telfeedate,'mm'),'03',a.factration))AS MAR,
SUM(decode(TO_CHAR(a.telfeedate,'mm'),'04',a.factration))AS APR,
SUM(decode(TO_CHAR(a.telfeedate,'mm'),'05',a.factration))AS MAY,
SUM(decode(TO_CHAR(a.telfeedate,'mm'),'06',a.factration))AS JUE,
SUM(decode(TO_CHAR(a.telfeedate,'mm'),'07',a.factration))AS JUL,
SUM(decode(TO_CHAR(a.telfeedate,'mm'),'08',a.factration))AS AGU,
SUM(decode(TO_CHAR(a.telfeedate,'mm'),'09',a.factration))AS SEP,
SUM(decode(TO_CHAR(a.telfeedate,'mm'),'10',a.factration))AS OCT,
SUM(decode(TO_CHAR(a.telfeedate,'mm'),'11',a.factration))AS NOV,
SUM(decode(TO_CHAR(a.telfeedate,'mm'),'12',a.factration))AS DEC
FROM (SELECT a.userper,a.tel,a.standfee,b.telfeedate,b.factration
FROM TELFEESTAND a,TELFEE b
WHERE a.tel =b.telfax)a
GROUP BY a.userper,a.tel,a.standfee,TO_CHAR(a.telfeedate,'yyyy')
8.说明：四表联查问题：
SQL:select *from a left inner join b on a.a=b.b
right inner join c on a.a=c.c inner join d on a.a=d.d where .....
9.说明：得到表中最小的未使用的ID号
SQL:
SELECT (CASE WHEN EXISTS(SELECT
*FROM Handle b WHERE b.HandleID =1)THEN MIN(HandleID)+1ELSE 1END)as
HandleID
FROM Handle
WHERE NOT HandleID IN (SELECT a.HandleID -
1FROM Handle a)
9.SQL语句技巧
9.1、一个SQL语句的问题:行列转换
select *
from v_temp
上面的视图结果如下:
user_name
role_name
-------------------------
系统管理员管理员
feng 管理员
feng 一般用户
test 一般用户
想把结果变成这样:
user_name
role_name
---------------------------
系统管理员管理员
feng 管理员,一般用户
test
一般用户
===================
create table a_test(name varchar(20),role2
varchar(20))
insert into a_test values('李','管理員')
insert into a_test
values('張','管理員')
insert into a_test values('張','一般用戶')
insert into a_test
values('常','一般用戶')
create function join_str(@content
varchar(100))
returns varchar(2000)
as
begin
declare @str
varchar(2000)
set @str=''
select @str=@str+','+rtrim(role2)from a_test
where [name]=@content
select @str=right(@str,len(@str)-1)
return
@str
end
go
--调用：
select [name],dbo.join_str([name])role2from
a_test group by [name]
--select distinct name,dbo.uf_test(name)from
a_test
9.2、求助！快速比较结构相同的两表
结构相同的两表，一表有记录3万条左右，一表有记录2万条左右，我怎样快速查找两表的不同记录？
============================
给你一个测试方法，从northwind中的orders表取数据。
select
*into n1from orders
select *into n2from orders
select *from
n1
select *from n2
--添加主键，然后修改n1中若干字段的若干条
alter table n1add
constraint pk_n1_id primary key (OrderID)
alter table n2add constraint
pk_n2_id primary key (OrderID)
select OrderID from (select *from
n1
union
select *from n2)a group by OrderID having count(*)>
1
应该可以，而且将不同的记录的ID显示出来。
下面的适用于双方记录一样的情况，
select *from n1where
orderid in
(
select OrderID from (select *from n1
union
select *
from n2)a group by OrderID having count(*)>1
)
至于双方互不存在的记录是比较好处理的
--删除n1,n2中若干条记录
delete from n1where orderID in
('10728','10730')
delete from n2where orderID in
('11000','11001')
--*************************************************************
--
双方都有该记录却不完全相同
select *from n1where orderid in
(
select OrderID from
(select *from n1
union
select *from n2)a group by OrderID having
count(*)>1
)
union
--n2中存在但在n1中不存的在10728,10730
select *from n1
where OrderID not in (select OrderID from
n2)
union
--n1中存在但在n2中不存的在11000,11001
select *from n2where OrderID
not in (select OrderID from n1)
9.3、四种方法取表里n到m条纪录：
1.
select
top m *into 临时表(或表变量)from tablename order by columnname --将top m笔插入
set
rowcount n
select *from 表变量order by columnname desc
2.
select
top n *from
(select top m *from tablename order by columnname)a
order
by columnname desc
3.如果tablename里没有其他identity列，那么：
select
identity(int)id0,*into #temp from tablename
取n到m条的语句为：
select *from
#temp where id0>=n and id0<=m
如果你在执行select identity(int)id0,*
into #temp from tablename这条语句的时候报错,那是因为你的DB中间的select
into/bulkcopy属性没有打开要先执行：
exec sp_dboption 你的DB名字,'select
into/bulkcopy',true
4.如果表里有identity属性，那么简单：
select *from
tablename where identitycol between n and m
5.如何删除一个表中重复的记录？
create table
a_dist(id int,name varchar(20))
insert into a_dist
values(1,'abc')
insert into a_dist values(1,'abc')
insert into a_dist
values(1,'abc')
insert into a_dist values(1,'abc')
exec up_distinct
'a_dist','id'
select *from a_dist
create procedure
up_distinct(@t_name varchar(30),@f_key
varchar(30))
--f_key表示是分組字段﹐即主鍵字段
as
begin
declare @max integer,@id
varchar(30),@sql varchar(7999),@type integer
select @sql ='declare
cur_rows cursor for select '+@f_key+',count(*)from '+@t_name +'group by '
+@f_key +'having count(*)>1'
exec(@sql)
open cur_rows
fetch
cur_rows into @id,@max
while @@fetch_status=0
begin
select @max =
@max -1
set rowcount @max
select @type =xtype from syscolumns where
id=object_id(@t_name)and name=@f_key
if @type=56
select @sql ='delete
from '+@t_name+'where '+@f_key+'='+@id
if @type=167
select @sql =
'delete from '+@t_name+'where '+@f_key+'='+''''+@id +''''
exec(@sql)
fetch cur_rows into @id,@max
end
close cur_rows
deallocate cur_rows
set rowcount 0
end
select *from
systypes
select *from syscolumns where id =
object_id('a_dist')
9.4.查询数据的最大排序问题（只能用一条语句写）
CREATE TABLE hard (qu
char (11),co char (11),je numeric(3,0))
insert into hard values
('A','1',3)
insert into hard values ('A','2',4)
insert into hard values
('A','4',2)
insert into hard values ('A','6',9)
insert into hard values
('B','1',4)
insert into hard values ('B','2',5)
insert into hard values
('B','3',6)
insert into hard values ('C','3',4)
insert into hard values
('C','6',7)
insert into hard values
('C','2',3)
要求查询出来的结果如下：
qu co je
----------------------
-----
A 69
A 24
B 36
B 25
C 67
C 3
4
就是要按qu分组，每组中取je最大的前2位！！
而且只能用一句sql语句！！！
select *from hard a
where je in (select top 2je from hard b where a.qu=b.qu order by je)
9.5.求删除重复记录的sql语句？
怎样把具有相同字段的纪录删除，只留下一条。
例如，表test里有id,name字段
如果有name相同的记录
只留下一条，其余的删除。
name的内容不定，相同的记录数不定。
有没有这样的sql语句？ it is very useful
thank you a lot 未有時間詳閱但已存檔 .. thank you :smilies54:
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