如何在 SQL Server 中循环一组记录？

Question

如何从 select 语句循环访问一组记录？

假设我有一些记录，我希望循环遍历并对每条记录执行一些操作。这是我的 select 语句的原始版本：

select top 1000 * from dbo.table
where StatusID = 7

Answer 1

通过使用 T-SQL 和游标，如下所示：

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;

Answer 2

如果您需要进行迭代，这就是我一直在做的事情......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

Answer 3

对 sam yi 的答案进行小改动（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

Answer 4

通过使用光标，您可以轻松地单独迭代记录并单独打印记录或作为包含所有记录的单个消息。

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

Answer 5

如果您可以使用临时表，这只是另一种方法。我亲自测试过这一点，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

Answer 6

您可以选择对数据进行排名并添加 ROW_NUMBER 并在迭代数据集时倒数至零。

-- 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

Answer 7

这样我们就可以迭代表数据。

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格。谢谢

Answer 8

这里是对 FloChanz 得票最高的答案的一个小改进：仅使用一个“FETCH”语句。这样就可以更轻松地添加新列，并且可以避免意外地让 FETCH 执行两项不同的操作：

/*
create table my_table (yourfield varchar(100), statusid int)
insert into my_Table select 'abc', 7
insert into my_Table select 'pdq', 6
insert into my_Table select 'xyz', 7
*/
DECLARE @MyCursor CURSOR;
DECLARE @MyField varchar(100);
DECLARE @finished bit = 0
BEGIN
    SET @MyCursor = CURSOR FOR
    select top 1000 YourField from dbo.my_table
        where StatusID = 7

    OPEN @MyCursor
    while @finished = 0 begin
      FETCH NEXT FROM @MyCursor
      INTO @MyField
      if @@FETCH_STATUS = 0
      BEGIN
        /*
           YOUR ALGORITHM GOES HERE
        */
        print @MyField
      end else begin
        set @finished = 1
      END;
    END;

    CLOSE @MyCursor ;
    DEALLOCATE @MyCursor;
END;

Answer 9

我认为这是迭代项目的简单方法示例。

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