如何从选择语句循环遍历一组记录?
假设我有一些记录,我希望对它们进行循环,并对每个记录执行一些操作。下面是我的select语句的原始版本:
select top 1000 * from dbo.table
where StatusID = 7
如何从选择语句循环遍历一组记录?
假设我有一些记录,我希望对它们进行循环,并对每个记录执行一些操作。下面是我的select语句的原始版本:
select top 1000 * from dbo.table
where StatusID = 7
当前回答
对sam yi的答案做个小改动(为了更好的可读性):
select top 1000 TableID
into #ControlTable
from dbo.table
where StatusID = 7
declare @TableID int
while exists (select * from #ControlTable)
begin
select @TableID = (select top 1 TableID
from #ControlTable
order by TableID asc)
-- Do something with your TableID
delete #ControlTable
where TableID = @TableID
end
drop table #ControlTable
其他回答
如果您喜欢使用临时表,这是另一种方法。我亲自测试了这个,它不会导致任何异常(即使临时表没有任何数据)。
CREATE TABLE #TempTable
(
ROWID int identity(1,1) primary key,
HIERARCHY_ID_TO_UPDATE int,
)
--create some testing data
--INSERT INTO #TempTable VALUES(1)
--INSERT INTO #TempTable VALUES(2)
--INSERT INTO #TempTable VALUES(4)
--INSERT INTO #TempTable VALUES(6)
--INSERT INTO #TempTable VALUES(8)
DECLARE @MAXID INT, @Counter INT
SET @COUNTER = 1
SELECT @MAXID = COUNT(*) FROM #TempTable
WHILE (@COUNTER <= @MAXID)
BEGIN
--DO THE PROCESSING HERE
SELECT @HIERARCHY_ID_TO_UPDATE = PT.HIERARCHY_ID_TO_UPDATE
FROM #TempTable AS PT
WHERE ROWID = @COUNTER
SET @COUNTER = @COUNTER + 1
END
IF (OBJECT_ID('tempdb..#TempTable') IS NOT NULL)
BEGIN
DROP TABLE #TempTable
END
通过使用T-SQL和像这样的游标:
DECLARE @MyCursor CURSOR;
DECLARE @MyField YourFieldDataType;
BEGIN
SET @MyCursor = CURSOR FOR
select top 1000 YourField from dbo.table
where StatusID = 7
OPEN @MyCursor
FETCH NEXT FROM @MyCursor
INTO @MyField
WHILE @@FETCH_STATUS = 0
BEGIN
/*
YOUR ALGORITHM GOES HERE
*/
FETCH NEXT FROM @MyCursor
INTO @MyField
END;
CLOSE @MyCursor ;
DEALLOCATE @MyCursor;
END;
这就是我一直在做的,如果你需要做一些迭代…但首先寻找集合操作是明智的。另外,不要这样做,因为您不想学习游标。
select top 1000 TableID
into #ControlTable
from dbo.table
where StatusID = 7
declare @TableID int
while exists (select * from #ControlTable)
begin
select top 1 @TableID = TableID
from #ControlTable
order by TableID asc
-- Do something with your TableID
delete #ControlTable
where TableID = @TableID
end
drop table #ControlTable
这样我们就可以迭代到表数据。
DECLARE @_MinJobID INT
DECLARE @_MaxJobID INT
CREATE TABLE #Temp (JobID INT)
INSERT INTO #Temp SELECT * FROM DBO.STRINGTOTABLE(@JobID,',')
SELECT @_MinJID = MIN(JobID),@_MaxJID = MAX(JobID) FROM #Temp
WHILE @_MinJID <= @_MaxJID
BEGIN
INSERT INTO Mytable
(
JobID,
)
VALUES
(
@_MinJobID,
)
SET @_MinJID = @_MinJID + 1;
END
DROP TABLE #Temp
STRINGTOTABLE是用户定义函数,它将解析逗号分隔的数据并返回表。谢谢
对sam yi的答案做个小改动(为了更好的可读性):
select top 1000 TableID
into #ControlTable
from dbo.table
where StatusID = 7
declare @TableID int
while exists (select * from #ControlTable)
begin
select @TableID = (select top 1 TableID
from #ControlTable
order by TableID asc)
-- Do something with your TableID
delete #ControlTable
where TableID = @TableID
end
drop table #ControlTable