无论如何要遍历 T-SQL 中的表变量吗？
DECLARE @table1 TABLE ( col1 int )
INSERT into @table1 SELECT col1 FROM table2
我也使用游标，但游标似乎不如表变量灵活。
DECLARE cursor1 CURSOR
FOR SELECT col1 FROM table2
OPEN cursor1
FETCH NEXT FROM cursor1
我希望能够以与游标相同的方式使用表变量。这样，我可以在过程的一部分中对表变量执行一些查询，然后为表变量中的每一行执行一些代码。
任何帮助是极大的赞赏。
为您的表变量添加一个标识，然后从 1 到 INSERT-SELECT 的@@ROWCOUNT 进行简单循环。
试试这个：
DECLARE @RowsToProcess int
DECLARE @CurrentRow int
DECLARE @SelectCol1 int
DECLARE @table1 TABLE (RowID int not null primary key identity(1,1), col1 int )
INSERT into @table1 (col1) SELECT col1 FROM table2
SET @RowsToProcess=@@ROWCOUNT
SET @CurrentRow=0
WHILE @CurrentRow<@RowsToProcess
BEGIN
SET @CurrentRow=@CurrentRow+1
SELECT
@SelectCol1=col1
FROM @table1
WHERE RowID=@CurrentRow
--do your thing here--
END
DECLARE @table1 TABLE (
idx int identity(1,1),
col1 int )
DECLARE @counter int
SET @counter = 1
WHILE(@counter < SELECT MAX(idx) FROM @table1)
BEGIN
DECLARE @colVar INT
SELECT @colVar = col1 FROM @table1 WHERE idx = @counter
-- Do your work here
SET @counter = @counter + 1
END
信不信由你，这实际上比使用游标更高效、更高效。
我的两分钱..从KM.的回答中，如果您想删除一个变量，您可以对@RowsToProcess 进行倒计时而不是向上计数。
DECLARE @RowsToProcess int;
DECLARE @table1 TABLE (RowID int not null primary key identity(1,1), col1 int )
INSERT into @table1 (col1) SELECT col1 FROM table2
SET @RowsToProcess = @@ROWCOUNT
WHILE @RowsToProcess > 0 -- Countdown
BEGIN
SELECT *
FROM @table1
WHERE RowID=@RowsToProcess
--do your thing here--
SET @RowsToProcess = @RowsToProcess - 1; -- Countdown
END
您可以循环遍历表变量，也可以通过光标浏览它。这就是我们通常所说的 RBAR - 发音为 Reebar，意思是 Row-By-Agonizing-Row。
我建议为您的问题找到一个基于 SET 的答案（我们可以提供帮助）并尽可能远离 rbars。
看起来像这个演示：
DECLARE @vTable TABLE (IdRow int not null primary key identity(1,1),ValueRow int);
-------Initialize---------
insert into @vTable select 345;
insert into @vTable select 795;
insert into @vTable select 565;
---------------------------
DECLARE @cnt int = 1;
DECLARE @max int = (SELECT MAX(IdRow) FROM @vTable);
WHILE @cnt <= @max
BEGIN
DECLARE @tempValueRow int = (Select ValueRow FROM @vTable WHERE IdRow = @cnt);
---work demo----
print '@tempValueRow:' + convert(varchar(10),@tempValueRow);
print '@cnt:' + convert(varchar(10),@cnt);
print'';
--------------
set @cnt = @cnt+1;
END
没有 idRow 的版本，使用 ROW_NUMBER
DECLARE @vTable TABLE (ValueRow int);
-------Initialize---------
insert into @vTable select 345;
insert into @vTable select 795;
insert into @vTable select 565;
---------------------------
DECLARE @cnt int = 1;
DECLARE @max int = (select count(*) from @vTable);
WHILE @cnt <= @max
BEGIN
DECLARE @tempValueRow int = (
select ValueRow
from (select ValueRow
, ROW_NUMBER() OVER(ORDER BY (select 1)) as RowId
from @vTable
) T1
where t1.RowId = @cnt
);
---work demo----
print '@tempValueRow:' + convert(varchar(10),@tempValueRow);
print '@cnt:' + convert(varchar(10),@cnt);
print'';
--------------
set @cnt = @cnt+1;
END
这是我的变种。几乎就像所有其他人一样，但我只使用一个变量来管理循环。
DECLARE
@LoopId int
,@MyData varchar(100)
DECLARE @CheckThese TABLE
(
LoopId int not null identity(1,1)
,MyData varchar(100) not null
)
INSERT @CheckThese (MyData)
select MyData from MyTable
order by DoesItMatter
SET @LoopId = @@rowcount
WHILE @LoopId > 0
BEGIN
SELECT @MyData = MyData
from @CheckThese
where LoopId = @LoopId
-- Do whatever
SET @LoopId = @LoopId - 1
END
Raj More 的观点是相关的——只有在必要时才执行循环。
这是另一个答案，类似于贾斯汀的答案，但不需要身份或聚合，只需一个主（唯一）密钥。
declare @table1 table(dataKey int, dataCol1 varchar(20), dataCol2 datetime)
declare @dataKey int
while exists select 'x' from @table1
begin
select top 1 @dataKey = dataKey
from @table1
order by /*whatever you want:*/ dataCol2 desc
-- do processing
delete from @table1 where dataKey = @dataKey
end
我不知道 WHILE 结构。
但是，带有表变量的 WHILE 结构看起来类似于使用 CURSOR，因为您仍然必须根据行 IDENTITY 将行选择到变量中，这实际上是一个 FETCH。
使用 WHERE 和以下类似的东西有什么区别吗？
DECLARE @table1 TABLE ( col1 int )
INSERT into @table1 SELECT col1 FROM table2
DECLARE cursor1 CURSOR
FOR @table1
OPEN cursor1
FETCH NEXT FROM cursor1
我不知道这是否可能。我想你可能必须这样做：
DECLARE cursor1 CURSOR
FOR SELECT col1 FROM @table1
OPEN cursor1
FETCH NEXT FROM cursor1
谢谢你的帮助！
这是我的相同解决方案的版本...
declare @id int
SELECT @id = min(fPat.PatientID)
FROM tbPatients fPat
WHERE (fPat.InsNotes is not null AND DataLength(fPat.InsNotes)>0)
while @id is not null
begin
SELECT fPat.PatientID, fPat.InsNotes
FROM tbPatients fPat
WHERE (fPat.InsNotes is not null AND DataLength(fPat.InsNotes)>0) AND fPat.PatientID=@id
SELECT @id = min(fPat.PatientID)
FROM tbPatients fPat
WHERE (fPat.InsNotes is not null AND DataLength(fPat.InsNotes)>0)AND fPat.PatientID>@id
end
以下存储过程循环遍历表变量并按升序打印它。此示例使用 WHILE LOOP。
CREATE PROCEDURE PrintSequenceSeries
-- Add the parameters for the stored procedure here
@ComaSeperatedSequenceSeries nVarchar(MAX)
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;
DECLARE @SERIES_COUNT AS INTEGER
SELECT @SERIES_COUNT = COUNT(*) FROM PARSE_COMMA_DELIMITED_INTEGER(@ComaSeperatedSequenceSeries, ',') --- ORDER BY ITEM DESC
DECLARE @CURR_COUNT AS INTEGER
SET @CURR_COUNT = 1
DECLARE @SQL AS NVARCHAR(MAX)
WHILE @CURR_COUNT <= @SERIES_COUNT
BEGIN
SET @SQL = 'SELECT TOP 1 T.* FROM ' +
'(SELECT TOP ' + CONVERT(VARCHAR(20), @CURR_COUNT) + ' * FROM PARSE_COMMA_DELIMITED_INTEGER( ''' + @ComaSeperatedSequenceSeries + ''' , '','') ORDER BY ITEM ASC) AS T ' +
'ORDER BY T.ITEM DESC '
PRINT @SQL
EXEC SP_EXECUTESQL @SQL
SET @CURR_COUNT = @CURR_COUNT + 1
END;
以下语句执行存储过程：
EXEC PrintSequenceSeries '11,2,33,14,5,60,17,98,9,10'
SQL Query 窗口中显示的结果如下所示：
返回 TABLE 变量的函数 PARSE_COMMA_DELIMITED_INTEGER() 如下所示：
CREATE FUNCTION [dbo].[parse_comma_delimited_integer]
(
@LIST VARCHAR(8000),
@DELIMITER VARCHAR(10) = ',
'
)
-- TABLE VARIABLE THAT WILL CONTAIN VALUES
RETURNS @TABLEVALUES TABLE
(
ITEM INT
)
AS
BEGIN
DECLARE @ITEM VARCHAR(255)
/* LOOP OVER THE COMMADELIMITED LIST */
WHILE (DATALENGTH(@LIST) > 0)
BEGIN
IF CHARINDEX(@DELIMITER,@LIST) > 0
BEGIN
SELECT @ITEM = SUBSTRING(@LIST,1,(CHARINDEX(@DELIMITER, @LIST)-1))
SELECT @LIST = SUBSTRING(@LIST,(CHARINDEX(@DELIMITER, @LIST) +
DATALENGTH(@DELIMITER)),DATALENGTH(@LIST))
END
ELSE
BEGIN
SELECT @ITEM = @LIST
SELECT @LIST = NULL
END
-- INSERT EACH ITEM INTO TEMP TABLE
INSERT @TABLEVALUES
(
ITEM
)
SELECT ITEM = CONVERT(INT, @ITEM)
END
RETURN
END
Select Top 1 无需任何顺序/顺序即可轻松解决。
Create Function Test_Range()
Returns
@Result Table (ID Int)
As
Begin
Declare @ID Varchar(10) = ''
Declare @Rows Int, @Row Int = 0
Declare @Num Int, @RangeTo Int
Declare @RangeTable Table (ID Varchar(10), RangeFrom Int, RangeTo Int)
Insert Into @RangeTable Values ('A', 1, 10)
Insert Into @RangeTable Values ('B', 25,30)
Set @Rows = (Select Count(*) From @RangeTable)
While @Row <= @Rows
Begin
Set @Row = @Row + 1
Select Top 1 @ID = ID, @Num = RangeFrom, @RangeTo = RangeTo From @RangeTable
Where ID > @ID
While @Num <= @RangeTo
Begin
Insert Into @Result Values (@Num)
Set @Num = @Num + 1
End
End
Return
End