sql實用語句（三）技巧
1、1=1，1=2的使用，在sql語句組合時用的較多
「where 1=1」 是表示選擇全部 「where 1=2」全部不選，
如：if @strwhere !=』』
begin
set @strsql = 『select count() as total from [』 + @tblname + '] where 』 + @strwhere
endelse
begin
set @strsql = 'select count() as total from [』 + @tblname + 『]』
end我們可以直接寫成
錯誤！未找到目錄項。
set @strsql = 『select count(*) as total from [』 + @tblname + '] where 1=1 安定 '+ @strwhere 2、收縮資料庫
–重建索引
dbcc reindex
dbcc indexdefrag
–收縮資料和日誌
dbcc shrinkdb
dbcc shrinkfile
3、壓縮資料庫
dbcc shrinkdatabase(dbname)
4、轉移資料庫給新使用者以已存在使用者許可權
exec sp_change_users_login 『update_one』,『newname』,『oldname』
go5、檢查備份集
restore verifyonly from disk=『e:\dvbbs.bak』
6、修復資料庫
alter database [dvbbs] set single_user
godbcc checkdb(『dvbbs』,repair_allow_data_loss) with tablock
goalter database [dvbbs] set multi_user
go7、日誌清除
set nocount on
declare @logicalfilename sysname,
@maxminutes int,
@newsize int
use tablename – 要操作的資料庫名
select @logicalfilename = 『tablename_log』, – 日誌檔名
@maxminutes = 10, – limit on time allowed to wrap log.
@newsize = 1 – 你想設定的日誌檔案的大小(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 < @originalsize / 16) and (@counter < 50000))
begin – update
insert dummytrans values (『fill log』) delete dummytrans
select @counter = @counter + 1
endexec (@trunclog)
endselect 'final size of 』 + db_name() + 』 log is 』 +
convert(varchar(30),size) + 』 8k pages or 』 +
convert(varchar(30),(size8/1024)) + 『mb』
from sysfiles
where name = @logicalfilename
drop table dummytrans
set nocount off
8、說明：更改某個表
exec sp_changeobjectowner 『tablename』,『dbo』
9、儲存更改全部表
create procedure dbo.user_changeobjectownerbatch
@oldowner as nvarchar(128),
@newowner as nvarchar(128)
asdeclare @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
endclose curobject
deallocate curobject
go10、sql server中直接迴圈寫入資料
declare @i int
set @i=1
while @i<30
begin
insert into test (userid) values(@i)
set @i=@i+1
end案例：
有如下表，要求就表中所有沒有及格的成績，在每次增長0.1的基礎上，使他們剛好及格:
name score
zhangshan 80
lishi 59
wangwu 50
songquan 69
while((select min(score) from tb_table)<60)
begin
update tb_table set score =score1.01
where score<60
if (select min(score) from tb_table)>60
break
else
continue
end
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