如何循环遍历从select语句返回的一组记录?
比方说我有几条记录希望逐一处理。下面是一个简单版本的select语句:
select top 1000 * from dbo.table
where StatusID = 7
如何循环遍历从select语句返回的一组记录?
比方说我有几条记录希望逐一处理。下面是一个简单版本的select语句:
select top 1000 * from dbo.table
where StatusID = 7
通过使用 T-SQL 和类似这样的光标:
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;
如果您需要进行重复操作,这就是我一直在做的事情……但是最好先查找集合操作。另外,请不要这样做,因为您不想学习光标。
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
WHILE
循环,CURSORS
通常需要更长的时间来完成相同的任务。 - undefined对sam yi的回答进行了小改动(以提高可读性):
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
DECLARE @CustomerID as INT;
declare @msg varchar(max)
DECLARE @BusinessCursor as CURSOR;
SET @BusinessCursor = CURSOR FOR
SELECT CustomerID FROM Customer WHERE CustomerID IN ('3908745','3911122','3911128','3911421')
OPEN @BusinessCursor;
FETCH NEXT FROM @BusinessCursor INTO @CustomerID;
WHILE @@FETCH_STATUS = 0
BEGIN
SET @msg = '{
"CustomerID": "'+CONVERT(varchar(10), @CustomerID)+'",
"Customer": {
"LastName": "LastName-'+CONVERT(varchar(10), @CustomerID) +'",
"FirstName": "FirstName-'+CONVERT(varchar(10), @CustomerID)+'",
}
}|'
print @msg
FETCH NEXT FROM @BusinessCursor INTO @CustomerID;
END
-- Get your dataset and rank your dataset by adding a new row_number
SELECT TOP 1000 A.*, ROW_NUMBER() OVER(ORDER BY A.ID DESC) AS ROW
INTO #TEMPTABLE
FROM DBO.TABLE AS A
WHERE STATUSID = 7;
--Find the highest number to start with
DECLARE @COUNTER INT = (SELECT MAX(ROW) FROM #TEMPTABLE);
DECLARE @ROW INT;
-- Loop true your data until you hit 0
WHILE (@COUNTER != 0)
BEGIN
SELECT @ROW = ROW
FROM #TEMPTABLE
WHERE ROW = @COUNTER
ORDER BY ROW DESC
--DO SOMTHING COOL
-- SET your counter to -1
SET @COUNTER = @ROW -1
END
DROP TABLE #TEMPTABLE
如果您可以使用临时表,这是另一种方法。我个人测试过,即使临时表没有任何数据,也不会引发任何异常。
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
COUNT(*)
,第二个从COUNT(*)
到1也很奇怪。 - David Ferenczy RogožanWHILE (@COUTNER <= @ROWID)
,而无需在每次迭代中递减 @ROWID
。顺便问一下,如果你的表中的 ROWID
不连续(之前删除了某些行),会发生什么? - David Ferenczy RogožanDECLARE @_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 是一个用户自定义函数,用于解析逗号分隔的数据并返回表格。谢谢。
我认为这是迭代项目的简单示例。
declare @cateid int
select CateID into [#TempTable] from Category where GroupID = 'STOCKLIST'
while (select count(*) from #TempTable) > 0
begin
select top 1 @cateid = CateID from #TempTable
print(@cateid)
--DO SOMETHING HERE
delete #TempTable where CateID = @cateid
end
drop table #TempTable