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sql server 的遊標

使用 left dbo 遊標 刪除 first 目標 沒有 prior

-- sql server 中的遊標

--聲明遊標

/*

declare cursorname [insensitive] [scroll] cursor

for <select-查詢塊>

[for {read only|update[of<列名>[,...,n]]}]

Insensitive 表示把取出來的數據存入一個在tempdb庫中創建的臨時表,任何通過這個遊標進行的操作,都會在這個臨時表裏進行。所有對基本表的改動都不會在用遊標進行的操作中體現出來,不用該關鍵字,則用戶對基本表所進行的任何操作都將在遊標中得到體現。

Scroll: 指定所有的提取選項(first,last,prior,wext,relative,absolute)均可用,允許刪除和更新(假定沒有使用insensitive選項)

for read only :遊標只讀。不允許通過只讀遊標進行數據的更新。

for update[of <列名>[,...,n]]:遊標是可修改的。定義在這個遊標裏可以更新的列。如果定義了[of<列名>[,...n]],則只有其中的列可以被修改;否則,遊標裏的所有列都可以被修改。

*/

declare @tagname nvarchar(max)

declare @max_datetime datetime

declare mycursor cursor

for

select a.tagname,max(isnull(b.DateTime,0))

from tblfminfolive a

left join live_dblink.gb_scada_live.dbo.LiveData b on a.tagname=b.tagname and b.provider=‘TAX‘

group by a.tagname;

-- 打開遊標

open mycursor;

-- 提取數據

-- fetch[[next|prior|first|last|absoute n|relative n] from] <遊標名> [into @變量名[,...,n]]

fetch next from mycursor into @tagname,@max_datetime;

/*全局變量@@fetch_status表示fetch語句的狀態

0 表示提取正常

1 表示已經取到了數據集的末尾

其他值均表明操作出了問題

*/

-- 進入循環

while (@@fetch_status=0)

BEGIN

IF right(@tagname,2) !=‘YL‘

-- 寫入flux,PlusTotalFlux,ReverseTotalFlux to 目標表

insert into live_dblink.gb_scada_live.dbo.LiveData(

provider,sitename,tagname,MeterName,DateTime,value)

select ‘TAX‘,b.username,b.tagname,b.MeterName,a.readtime

,case right(@tagname,2)

when ‘SL‘ then a.flux

when ‘ZL‘ then a.plustotalflux

when ‘FL‘ then a.reversetotalflux

end

FROM tblfmreaddata a ,tblfminfolive b

WHERE a.fmaddress+right(@tagname,3)=@tagname and b.tagname=@tagname

AND a.readtime>@max_datetime

ELSE

--寫入 pressure to 目標表

insert into live_dblink.gb_scada_live.dbo.LiveData(

provider,sitename,tagname,MeterName,DateTime,value)

select ‘TAX‘,b.username,b.tagname,b.MeterName,a.readtime,isnull(a.pressure,0)

FROM tblfmreaddatapress a,tblfminfolive b

WHERE a.fmaddress+right(@tagname,3)=@tagname and b.tagname=@tagname

AND a.readtime>@max_datetime

-- 獲取下一條數據

fetch next from mycusor into @tagname,@max_datetime;

END;

-- 關閉遊標

close mycursor;

-- 釋放遊標

deallocate mycursor;

-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--- 由於sql server 的未知原因,cursor未能成功執行,於是創建臨時表,原理類似cursor,如下:

--------------------------------------------------------------------------------

declare @cun int

declare @maxcun int

declare @max_datetime datetime

declare @fmaddress varchar(40)

create table #tmp_fmaddress

(

pid int identity(1,1),

fmaddress varchar(100),

max_datetime datetime

)

insert into #tmp_fmaddress(fmaddress,max_datetime)

select a.fmaddress,max(isnull(b.DateTime,0))

from tblfminfolive a

left join live_dblink.gb_scada_live.dbo.LiveData b on a.tagname=b.tagname and b.provider=‘TAX‘

and b.DateTime>dateadd(day,-2,getdate())

group by a.fmaddress

set @cun=1

select @maxcun=max(pid) from #tmp_fmaddress

-- 進入循環

while @cun<@maxcun+1

BEGIN

select @fmaddress=fmaddress,@max_datetime=max_datetime from #tmp_fmaddress where pid=@cun

------流量數據

select fmaddress,readtime,flux,PlusTotalFlux,ReverseTotalFlux

into #temp_flux

FROM tblfmreaddata WHERE fmaddress=@fmaddress

AND readtime>@max_datetime

AND readtime>dateadd(day,-2,getdate())

-----壓力數據

select fmaddress,readtime, isnull(pressure,0) press

into #temp_press

FROM tblfmreaddatapress WHERE fmaddress=@fmaddress

AND readtime>@max_datetime

and readtime>dateadd(day,-2,getdate())

-- 寫入flux,PlusTotalFlux,ReverseTotalFlux to 目標表

insert into live_dblink.gb_scada_live.dbo.LiveData(

provider,sitename,tagname,MeterName,DateTime,value)

select ‘TAX‘,b.username,b.tagname,b.MeterName,a.readtime

,case right(b.tagname,2)

when ‘SL‘ then a.flux

when ‘ZL‘ then a.plustotalflux

when ‘FL‘ then a.reversetotalflux

end

FROM #temp_flux a,tblfminfolive b

where a.fmaddress=b.fmaddress and b.tagname!=@fmaddress+‘_YL‘

-- 寫入 pressure

insert into live_dblink.gb_scada_live.dbo.LiveData(

provider,sitename,tagname,MeterName,DateTime,value)

select ‘TAX‘,b.username,b.tagname,b.MeterName,a.readtime,a.press

FROM #temp_press a,tblfminfolive b

where a.fmaddress=b.fmaddress and b.tagname=@fmaddress+‘_YL‘

drop table #temp_flux

drop table #temp_press

-- 獲取下一條數據

set @cun=@cun+1

END

sql server 的遊標