sql操作技巧

1、1=1，1=2的使用，在SQL语句组合时用的较多
“where 1=1” 是表示选择全部 “where 1=2”全部不选，如：
if @strWhere !=''
begin
set @strSQL = 'select count(*) as Total from [' + @tblName + '] where ' + @strWhere
end
else
begin
set @strSQL = 'select count(*) as Total from [' + @tblName + ']'
end
我们可以直接写成
set @strSQL = 'select count(*) as Total from [' + @tblName + '] where 1=1 安定 '+ @strWhere
2、收缩数据库
--重建索引
DBCC REINDEX
DBCC INDEXDEFRAG
--收缩数据和日志
DBCC SHRINKDB
DBCC SHRINKFILE
3、压缩数据库
dbcc shrinkdatabase(dbname)
4、转移数据库给新用户以已存在用户权限
exec sp_change_users_login 'update_one','newname','oldname'
go
5、检查备份集
RESTORE VERIFYONLY from disk='E:dvbbs.bak'
6、修复数据库
ALTER DATABASE [dvbbs] SET SINGLE_USER
GO
DBCC CHECKDB('dvbbs',repair_allow_data_loss) WITH TABLOCK
GO
ALTER DATABASE [dvbbs] SET MULTI_USER
GO
7、日志清除
SET NOCOUNT ON
DECLARE @LogicalFileName sysname,
@MaxMinutes INT,
@NewSize INT
USE tablename -- 要操作的数据库名
SELECT @LogicalFileName = 'tablename_log', -- 日志文件名
@MaxMinutes = 10, -- Limit on time allowed to wrap log.
@NewSize = 1 -- 你想设定的日志文件的大小(M)
-- Setup / initialize
DECLARE @OriginalSize int
SELECT @OriginalSize = size
FROM sysfiles
WHERE name = @LogicalFileName
SELECT 'Original Size of ' + db_name() + ' LOG is ' +
CONVERT(VARCHAR(30),@OriginalSize) + ' 8K pages or ' +
CONVERT(VARCHAR(30),(@OriginalSize*8/1024)) + 'MB'
FROM sysfiles
WHERE name = @LogicalFileName
CREATE TABLE DummyTrans
(DummyColumn char (8000) not null)
DECLARE @Counter INT,
@StartTime DATETIME,
@TruncLog VARCHAR(255)
SELECT @StartTime = GETDATE(),
@TruncLog = 'BACKUP LOG ' + db_name() + ' WITH TRUNCATE_ONLY'
DBCC SHRINKFILE (@LogicalFileName, @NewSize)
EXEC (@TruncLog)
-- Wrap the log if necessary.
WHILE @MaxMinutes > DATEDIFF (mi, @StartTime, GETDATE()) -- time has not expired
AND @OriginalSize = (SELECT size FROM sysfiles WHERE name = @LogicalFileName)
AND (@OriginalSize * 8 /1024) > @NewSize
BEGIN -- Outer loop.
SELECT @Counter = 0
WHILE ((@Counter BEGIN -- update
INSERT DummyTrans VALUES ('Fill Log')
DELETE DummyTrans
SELECT @Counter = @Counter + 1
END
EXEC (@TruncLog)
END
SELECT 'Final Size of ' + db_name() + ' LOG is ' +
CONVERT(VARCHAR(30),size) + ' 8K pages or ' +
CONVERT(VARCHAR(30),(size*8/1024)) + 'MB'
FROM sysfiles
WHERE name = @LogicalFileName
DROP TABLE DummyTrans
SET NOCOUNT OFF
8、说明：更改某个表
exec sp_changeobjectowner 'tablename','dbo'
9、存储更改全部表
CREATE PROCEDURE dbo.User_ChangeObjectOwnerBatch
@OldOwner as NVARCHAR(128),
@NewOwner as NVARCHAR(128)
AS
DECLARE @Name as NVARCHAR(128)
DECLARE @Owner as NVARCHAR(128)
DECLARE @OwnerName as NVARCHAR(128)
DECLARE curObject CURSOR FOR
select 'Name' = name,
'Owner' = user_name(uid)
from sysobjects
where user_name(uid)=@OldOwner
order by name
OPEN curObject
FETCH NEXT FROM curObject INTO @Name, @Owner
WHILE(@@FETCH_STATUS=0)
BEGIN
if @Owner=@OldOwner
begin
set @OwnerName = @OldOwner + '.' + rtrim(@Name)
exec sp_changeobjectowner @OwnerName, @NewOwner
end
-- select @name,@NewOwner,@OldOwner
FETCH NEXT FROM curObject INTO @Name, @Owner
END
close curObject
deallocate curObject
GO
10、SQL SERVER中直接循环写入数据
declare @i int
set @i=1
while @ibegin
insert into test (userid) values(@i)
set @i=@i+1
end

小记存储过程中经常用到的本周，本月，本年函数
Dateadd(wk,datediff(wk,0,getdate()),-1)
Dateadd(wk,datediff(wk,0,getdate()),6)
Dateadd(mm,datediff(mm,0,getdate()),0)
Dateadd(ms,-3,dateadd(mm,datediff(m,0,getdate())+1,0))
Dateadd(yy,datediff(yy,0,getdate()),0)
Dateadd(ms,-3,DATEADD(yy, DATEDIFF(yy,0,getdate())+1, 0))

上面的SQL代码只是一个时间段
Dateadd(wk,datediff(wk,0,getdate()),-1)
Dateadd(wk,datediff(wk,0,getdate()),6)
就是表示本周时间段.
下面的SQL的条件部分,就是查询时间段在本周范围内的:
Where Time BETWEEN Dateadd(wk,datediff(wk,0,getdate()),-1) AND Dateadd(wk,datediff(wk,0,getdate()),6)
而在存储过程中
select @begintime = Dateadd(wk,datediff(wk,0,getdate()),-1)
select @endtime = Dateadd(wk,datediff(wk,0,getdate()),6)

分组group
常用于统计时，如分组查总数：
select gender,count(sno)
from students
group by gender
(查看男女学生各有多少)
注意：从哪种角度分组就从哪列"group by"
对于多重分组，只需将分组规则罗列。比如查询各届各专业的男女同学人数 ，那么分组规则有：届别(grade)、专业(mno)和性别(gender)，所以有"group by grade, mno, gender"
select grade, mno, gender, count(*)
from students
group by grade, mno, gender
通常group还和having联用，比如查询1门课以上不及格的学生，则按学号(sno)分类有：
select sno,count(*) from grades
where markgroup by sno
having count(*)>1
6.UNION联合
合并查询结果，如：
SELECT * FROM students
WHERE name like ‘张%’
UNION [ALL]
SELECT * FROM students
WHERE name like ‘李%’
7.多表查询
a.内连接
select g.sno,s.name,c.coursename
from grades g JOIN students s ON g.sno=s.sno
JOIN courses c ON g.cno=c.cno
(注意可以引用别名)
b.外连接
b1.左连接
select courses.cno,max(coursename),count(sno)
from courses LEFT JOIN grades ON courses.cno=grades.cno
group by courses.cno
左连接特点：显示全部左边表中的所有项目，即使其中有些项中的数据未填写完全。
左外连接返回那些存在于左表而右表中却没有的行，再加上内连接的行。
b2.右连接
与左连接类似
b3.全连接
select sno,name,major
from students FULL JOIN majors ON students.mno=majors.mno
两边表中的内容全部显示
c.自身连接
select c1.cno,c1.coursename,c1.pno,c2.coursename
from courses c1,courses c2 where c1.pno=c2.cno
采用别名解决问题。
d.交叉连接
select lastname+firstname from lastname CROSS JOIN firstanme
Oracle维护常用SQL语句发布时间：2006-06-28 09:47     点击：9
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　　FROM SYS.SM$TS_AVAIL A,SYS.SM$TS_USED B,SYS.SM$TS_FREE C 
　　WHERE A.TABLESPACE_NAME=B.TABLESPACE_NAME AND A.TABLESPACE_NAME=C.TABLESPACE_NAME; 
7、查看数据库库对象 
　　select owner, object_type, status, count(*) count# from all_objects group by owner, object_type, status; 
8、查看数据库的版本
　　Select version FROM Product_component_version
　　Where SUBSTR(PRODUCT,1,6)=’Oracle’;
9、查看数据库的创建日期和归档方式
　　Select Created, Log_Mode, Log_Mode From V$Database; 
10、捕捉运行很久的SQL 
　　column username format a12 
　　column opname format a16
　　column progress format a8
　　select username,sid,opname, 
　　round(sofar*100 / totalwork,0) 　　 ’%’ as progress, 
　　time_remaining,sql_text 
　　from v$session_longops , v$sql
　　where time_remaining <> 0 
　　and sql_address = address
　　and sql_hash_value = hash_value
11、查看数据表的参数信息 　　
    SELECT partition_name, high_value, high_value_length, tablespace_name,
　　pct_free, pct_used, ini_trans, max_trans, initial_extent,
　　next_extent, min_extent, max_extent, pct_increase, FREELISTS,
　　freelist_groups, LOGGING, BUFFER_POOL, num_rows, blocks,
　　empty_blocks, avg_space, chain_cnt, avg_row_len, sample_size,
    last_analyzed
　　FROM dba_tab_partitions
　　--WHERE table_name = :tname AND table_owner = :towner
　　ORDER BY partition_position
12、查看还没提交的事务
　　select * from v$locked_object;
　　select * from v$transaction;
13、查找object为哪些进程所用
　　select
　　p.spid,
　　s.sid,
　　s.serial# serial_num,
　　s.username user_name,
　　a.type object_type,
　　s.osuser os_user_name,
　　a.owner,
　　a.object object_name,
　　decode(sign(48 - command),
　　1, to_char(command), 'Action Code #' 　　 to_char(command) ) action,
　　p.program oracle_process,
　　s.terminal terminal,
　　s.program program,
　　s.status session_status
　　from v$session s, v$access a, v$process p
　　where s.paddr = p.addr and
　　s.type = 'USER' and
　　a.sid = s.sid and
　　a.object='SUBSCRIBER_ATTR'
　　order by s.username, s.osuser
14、回滚段查看 　　
    select rownum, sys.dba_rollback_segs.segment_name Name, v$rollstat.extents
　　Extents, v$rollstat.rssize Size_in_Bytes, v$rollstat.xacts XActs,
　　v$rollstat.gets Gets, v$rollstat.waits Waits, v$rollstat.writes Writes,
　　sys.dba_rollback_segs.status status from v$rollstat, sys.dba_rollback_segs,
　　v$rollname where v$rollname.name(+) = sys.dba_rollback_segs.segment_name and
　　v$rollstat.usn (+) = v$rollname.usn order by rownum

15、耗资源的进程（top session）
　　select s.schemaname schema_name, decode(sign(48 - command), 1,
    to_char(command), 'Action Code #' 　　 to_char(command) ) action, status
　　session_status, s.osuser os_user_name, s.sid, p.spid , s.serial# serial_num,
　　nvl(s.username, '[Oracle process]') user_name, s.terminal terminal,
　　s.program program, st.value criteria_value from v$sesstat st, v$session s , v$processp
　　where st.sid = s.sid and st.statistic# = to_number('38') and ('ALL' = 'ALL'
　　or s.status = 'ALL') and p.addr = s.paddr order by st.value desc, p.spid asc, s.username asc, s.osuser asc