程式師世界 >> 數據庫知識 >> 其他數據庫知識 >> 更多數據庫知識 >> 精妙的SQL語句

精妙的SQL語句

編輯：更多數據庫知識

說明：復制表(只復制結構,源表名：a 新表名：b)
select * into b from a where 1<>1
說明：拷貝表(拷貝數據,源表名：a 目標表名：b)
insert into b(a, b, c) select d,e,f from b;
說明：顯示文章、提交人和最後回復時間
select a.title,a.username,b.adddate from table a,(select max(adddate) adddate from table where table.title=a.title) b
說明：外連接查詢(表名1：a 表名2：b)
select a.a, a.b, a.c, b.c, b.d, b.f from a LEFT OUT JOIN b ON a.a = b.c
說明：日程安排提前五分鐘提醒
select * from 日程安排 where datediff('minute',f開始時間,getdate())>5
說明：兩張關聯表，刪除主表中已經在副表中沒有的信息
delete from info where not exists ( select * from infobz where info.infid=infobz.infid )
說明：--

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
說明：--
select * from studentinfo where not exists(select * from student where studentinfo.id=student.id) and 系名稱='"&strdepartmentname&"' and 專業名稱='"&strprofessionname&"' order by 性別,生源地,高考總成績
從數據庫中去一年的各單位電話費統計(電話費定額賀電化肥清單兩個表來源）

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')
說明：四表聯查問題
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 .....
說明：得到表中最小的未使用的ID號
SELECT (CASE WHEN EXISTS(SELECT * FROM Handle b WHERE b.HandleID = 1) THEN MIN(HandleID) + 1 ELSE 1 END) as HandleID FROM Handle WHERE NOT HandleID IN (SELECT a.HandleID - 1 FROM Handle a)
一個SQL語句的問題:行列轉換
select * from v_temp
上面的視圖結果如下:
user_name role_name
-------------------------
系統管理員管理員
feng 管理員
feng 一般用戶
test 一般用戶
想把結果變成這樣:
user_name role_name
---------------------------
系統管理員管理員
feng 管理員,一般用戶
test 一般用戶
===================
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

--調用：
select [name],dbo.join_str([name]) role2 from a_test group by [name]

--select distinct name,dbo.uf_test(name) from a_test
快速比較結構相同的兩表
結構相同的兩表，一表有記錄3萬條左右，一表有記錄2萬條左右，我怎樣快速查找兩表的不同記錄？
============================
給你一個測試方法，從northwind中的orders表取數據。
select * into n1 from orders
select * into n2 from orders

select * from n1
select * from n2

--添加主鍵，然後修改n1中若干字段的若干條
alter table n1 add constraint pk_n1_id primary key (OrderID)
alter table n2 add constraint pk_n2_id primary key (OrderID)

select OrderID from (select * from n1 union select * from n2) a group by OrderID having count(*) > 1

應該可以，而且將不同的記錄的ID顯示出來。
下面的適用於雙方記錄一樣的情況，

select * from n1 where orderid in (select OrderID from (select * from n1 union select * from n2) a group by OrderID having count(*) > 1)
至於雙方互不存在的記錄是比較好處理的
--刪除n1,n2中若干條記錄
delete from n1 where orderID in ('10728','10730')
delete from n2 where orderID in ('11000','11001')

--*************************************************************
-- 雙方都有該記錄卻不完全相同
select * from n1 where 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 n2 where OrderID not in (select OrderID from n1)
四種方法取表裡n到m條紀錄：

1.
select top m * into 臨時表(或表變量) from tablename order by columnname -- 將top m筆插入
set rowcount n
select * from 表變量 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裡沒有其他identity列，那麼：
select identity(int) id0,* into #temp from tablename

取n到m條的語句為：
select * from #temp where id0 >=n and id0 <= m

如果你在執行select identity(int) id0,* into #temp from tablename這條語句的時候報錯,那是因為你的DB中間的select into/bulkcopy屬性沒有打開要先執行：
exec sp_dboption 你的DB名字,'select into/bulkcopy',true

4.如果表裡有identity屬性，那麼簡單：
select * from tablename where identitycol between n and m
如何刪除一個表中重復的記錄？
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')
查詢數據的最大排序問題（只能用一條語句寫）
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)

要求查詢出來的結果如下：

qu co je
----------- ----------- -----
A 6 9
A 2 4
B 3 6
B 2 5
C 6 7
C 3 4

就是要按qu分組，每組中取je最大的前2位！！
而且只能用一句sql語句！！！
select * from hard a where je in (select top 2 je from hard b where a.qu=b.qu order by je)
求刪除重復記錄的sql語句？
怎樣把具有相同字段的紀錄刪除，只留下一條。
例如，表test裡有id,name字段
如果有name相同的記錄只留下一條，其余的刪除。
name的內容不定，相同的記錄數不定。
有沒有這樣的sql語句？
==============================
A:一個完整的解決方案：

將重復的記錄記入temp1表:
select [標志字段id],count(*) into temp1 from [表名]
group by [標志字段id]
having count(*)>1

2、將不重復的記錄記入temp1表:
insert temp1 select [標志字段id],count(*) from [表名] group by [標志字段id] having count(*)=1

3、作一個包含所有不重復記錄的表：
select * into temp2 from [表名] where 標志字段id in(select 標志字段id from temp1)

4、刪除重復表:
delete [表名]

5、恢復表：
insert [表名] select * from temp2

6、刪除臨時表:
drop table temp1
drop table temp2
================================
B:
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')
行列轉換--普通

假設有張學生成績表(CJ)如下
Name Subject Result
張三語文 80
張三數學 90
張三物理 85
李四語文 85
李四數學 92
李四物理 82

想變成
姓名語文數學物理
張三 80 90 85
李四 85 92 82

declare @sql varchar(4000)
set @sql = 'select Name'
select @sql = @sql + ',sum(case Subject when '''+Subject+''' then Result end) ['+Subject+']'
from (select distinct Subject from CJ) as a
select @sql = @sql+' from test group by name'
exec(@sql)

行列轉換--合並

有表A,
id pid
1 1
1 2
1 3
2 1
2 2
3 1
如何化成表B:
id pid
1 1,2,3
2 1,2
3 1

創建一個合並的函數
create function fmerg(@id int)
returns varchar(8000)
as
begin
declare @str varchar(8000)
set @str=''
select @str=@str+','+cast(pid as varchar) from 表A where id=@id
set @str=right(@str,len(@str)-1)
return(@str)
End
go

--調用自定義函數得到結果
select distinct id,dbo.fmerg(id) from 表A
如何取得一個數據表的所有列名

方法如下：先從SYSTEMOBJECT系統表中取得數據表的SYSTEMID,然後再SYSCOLUMN表中取得該數據表的所有列名。
SQL語句如下：
declare @objid int,@objname char(40)
set @objname = 'tablename'
select @objid = id from sysobjects where id = object_id(@objname)
select 'Column_name' = name from syscolumns where id = @objid order by colid

或

SELECT * FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME ='users'
通過SQL語句來更改用戶的密碼

修改別人的,需要sysadmin role
EXEC sp_password NULL, 'newpassword', 'User'

如果帳號為SA執行EXEC sp_password NULL, 'newpassword', sa
怎麼判斷出一個表的哪些字段不允許為空？

select COLUMN_NAME from INFORMATION_SCHEMA.COLUMNS where IS_NULLABLE='NO' and TABLE_NAME=tablename
如何在數據庫裡找到含有相同字段的表？
a. 查已知列名的情況
SELECT b.name as TableName,a.name as columnname
From syscolumns a INNER JOIN sysobjects b
ON a.id=b.id
AND b.type='U'
AND a.name='你的字段名字'
未知列名查所有在不同表出現過的列名
Select o.name As tablename,s1.name As columnname
From syscolumns s1, sysobjects o
Where s1.id = o.id
And o.type = 'U'
And Exists (
Select 1 From syscolumns s2
Where s1.name = s2.name
And s1.id <> s2.id
)
查詢第xxx行數據

假設id是主鍵：
select * from (select top xxx * from yourtable) aa where not exists(select 1 from (select top xxx-1 * from yourtable) bb where aa.id=bb.id)

如果使用游標也是可以的
fetch absolute [number] from [cursor_name]
行數為絕對行數
SQL Server日期計算
a. 一個月的第一天
SELECT DATEADD(mm, DATEDIFF(mm,0,getdate()), 0)
b. 本周的星期一
SELECT DATEADD(wk, DATEDIFF(wk,0,getdate()), 0)
c. 一年的第一天
SELECT DATEADD(yy, DATEDIFF(yy,0,getdate()), 0)
d. 季度的第一天
SELECT DATEADD(qq, DATEDIFF(qq,0,getdate()), 0)
e. 上個月的最後一天
SELECT dateadd(ms,-3,DATEADD(mm, DATEDIFF(mm,0,getdate()), 0))
f. 去年的最後一天
SELECT dateadd(ms,-3,DATEADD(yy, DATEDIFF(yy,0,getdate()), 0))
g. 本月的最後一天
SELECT dateadd(ms,-3,DATEADD(mm, DATEDIFF(m,0,getdate())+1, 0))
h. 本月的第一個星期一
select DATEADD(wk, DATEDIFF(wk,0,
dateadd(dd,6-datepart(day,getdate()),getdate())
), 0)
i. 本年的最後一天
SELECT dateadd(ms,-3,DATEADD(yy, DATEDIFF(yy,0,getdate())+1, 0))。
獲取表結構[把 'sysobjects' 替換成 'tablename' 即可]

SELECT CASE IsNull(I.name, '')
When '' Then ''
Else '*'
End as IsPK,
Object_Name(A.id) as t_name,
A.name as c_name,
IsNull(SubString(M.text, 1, 254), '') as pbc_init,
T.name as F_DataType,
CASE IsNull(TYPEPROPERTY(T.name, 'Scale'), '')
WHEN '' Then Cast(A.prec as varchar)
ELSE Cast(A.prec as varchar) + ',' + Cast(A.scale as varchar)
END as F_Scale,
A.isnullable as F_isNullAble
FROM Syscolumns as A
JOIN Systypes as T
ON (A.xType = T.xUserType AND A.Id = Object_id('sysobjects') )
LEFT JOIN ( SysIndexes as I
JOIN Syscolumns as A1
ON ( I.id = A1.id and A1.id = object_id('sysobjects') and (I.status & 0x800) = 0x800 AND A1.colid <= I.keycnt) )
ON ( A.id = I.id AND A.name = index_col('sysobjects', I.indid, A1.colid) )
LEFT JOIN SysComments as M
ON ( M.id = A.cdefault and ObjectProperty(A.cdefault, 'IsConstraint') = 1 )
ORDER BY A.Colid ASC
提取數據庫內所有表的字段詳細說明的SQL語句

SELECT
(case when a.colorder=1 then d.name else '' end) N'表名',
a.colorder N'字段序號',
a.name N'字段名',
(case when COLUMNPROPERTY( a.id,a.name,'IsIdentity')=1 then '√'else ''
end) N'標識',
(case when (SELECT count(*)
FROM sysobjects
WHERE (name in
(SELECT name
FROM sysindexes
WHERE (id = a.id) AND (indid in
(SELECT indid
FROM sysindexkeys
WHERE (id = a.id) AND (colid in
(SELECT colid
FROM syscolumns
WHERE (id = a.id) AND (name = a.name))))))) AND
(xtype = 'PK'))>0 then '√' else '' end) N'主鍵',
b.name N'類型',
a.length N'占用字節數',
COLUMNPROPERTY(a.id,a.name,'PRECISION') as N'長度',
isnull(COLUMNPROPERTY(a.id,a.name,'Scale'),0) as N'小數位數',
(case when a.isnullable=1 then '√'else '' end) N'允許空',
isnull(e.text,'') N'默認值',
isnull(g.[value],'') AS N'字段說明'
FROM syscolumns a
left join systypes b
on a.xtype=b.xusertype
inner join sysobjects d
on a.id=d.id and d.xtype='U' and d.name<>'dtproperties'
left join syscomments e
on a.cdefault=e.id
left join sysproperties g
on a.id=g.id AND a.colid = g.smallid
order by object_name(a.id),a.colorder
快速獲取表test的記錄總數[對大容量表非常有效]

快速獲取表test的記錄總數:
select rows from sysindexes where id = object_id('test') and indid in (0,1)

update 2 set KHXH=(ID+1)\2 2行遞增編號
update [23] set id1 = 'No.'+right('00000000'+id,6) where id not like 'No%' //遞增
update [23] set id1= 'No.'+right('00000000'+replace(id1,'No.',''),6) //補位遞增
delete from [1] where (id%2)=1
奇數
替換表名字段
update [1] set domurl = replace(domurl,'Upload/Imgswf/','Upload/Photo/') where domurl like '%Upload/Imgswf/%'
截位
SELECT LEFT(表名, 5)