sql 光标重复

Question

我在 SQL 中使用的光标有问题。这是我第一次尝试使用它，但它似乎是无限重复第一个条目而不是遍历，我不确定为什么会这样，因为我的理解是 fetch next 语句应该继续循环。

输出显示为：

(235 row(s) affected)
95208

(1 row(s) affected)

(1 row(s) affected)
95208

(1 row(s) affected)

(1 row(s) affected)
95208

(1 row(s) affected)
...

如有任何帮助，我们将不胜感激。

这是我的脚本：

Disable trigger tr_ttcard_ForUpdate on ttcard

-- Loop through backupBoards
declare @getTBoard cursor
declare @getTCard cursor    
declare @tcardToUpdateId int

select ttboard.id into #TempTBoards from ttboard 
join newtbackuptboards on newtbackuptboards.TBoardId = ttboard.id
where ttboard.IsActive = 0 and newtbackuptboards.id is not null

-- Update each existing tcard in backupBoards to new mappings
set @getTCard = cursor for
select ttcard.id from ttcard 
join #TempTBoards on #TempTBoards.id = ttcard.parentboard
where #TempTBoards.id is not null

open @getTCard
fetch next from @getTCard into @tcardToUpdateId
while @@FETCH_STATUS = 0
begin
    print cast(@tcardToUpdateId as nvarchar(max))
    -- create new backupCardMap linking tcardId and backupId
    insert into tbackupTCardMap (backupTCardId, backupId)
    values(
        @tcardToUpdateId,
        (select newtbackuptboards.id from newtbackuptboards 
         join ttboard on ttboard.id = newtbackuptboards.TBoardId
         join ttcard on ttcard.parentboard = ttboard.id
         where ttcard.id = @tcardToUpdateId)
    )

    update ttcard
    set backupOfTCard = @tcardToUpdateId
    where id = @tcardToUpdateId

end
close @getTCard
deallocate @getTCard

drop table #TempTBoards
go
-- Enable trigger for tcard changes
Enable trigger tr_ttcard_ForUpdate on ttcard

Answer 1

您似乎在开始游标循环之前进行启动提取，但没有在循环内再次提取。在更新语句之后但在结束语句之前添加另一个提取。

update

Fetch Next

结束关闭

Answer 2

你错过了

fetch next from @getTCard into @tcardToUpdateId

见This

尝试：

open @getTCard
fetch next from @getTCard into @tcardToUpdateId
while @@FETCH_STATUS = 0
begin
    print cast(@tcardToUpdateId as nvarchar(max))
    -- create new backupCardMap linking tcardId and backupId
    insert into tbackupTCardMap (backupTCardId, backupId)
    values(
        @tcardToUpdateId,
        (select newtbackuptboards.id from newtbackuptboards 
         join ttboard on ttboard.id = newtbackuptboards.TBoardId
         join ttcard on ttcard.parentboard = ttboard.id
         where ttcard.id = @tcardToUpdateId)
    )

    update ttcard
    set backupOfTCard = @tcardToUpdateId
    where id = @tcardToUpdateId

fetch next from @getTCard into @tcardToUpdateId --what you missed 
end
close @getTCard
deallocate @getTCard

Answer 3

我会用简单的 INSERT 和 UPDATE 语句替换这个性能杀手游标，就像这样....

BEGIN TRANSACTION;

-- Update records
update ttcard
set backupOfTCard = ttboard.id
from ttboard 
join newtbackuptboards on newtbackuptboards.TBoardId = ttboard.id
join ttcard            on ttcard.parentboard = ttboard.id 
where ttboard.IsActive = 0 
  AND newtbackuptboards.id IS NOT NULL

-- Insert records
insert into tbackupTCardMap (backupTCardId, backupId)
SELECT ttboard.id , newtbackuptboards.id
from ttboard 
join newtbackuptboards on newtbackuptboards.TBoardId = ttboard.id
join ttcard            on ttcard.parentboard = ttboard.id 
where ttboard.IsActive = 0 
  AND newtbackuptboards.id IS NOT NULL

COMMIT TRANSACTION;

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