假设我有以下简单的表变量:
declare @databases table
(
DatabaseID int,
Name varchar(15),
Server varchar(15)
)
-- insert a bunch rows into @databases
如果我想遍历各行,声明和使用游标是我唯一的选择吗?还有别的办法吗?
假设我有以下简单的表变量:
declare @databases table
(
DatabaseID int,
Name varchar(15),
Server varchar(15)
)
-- insert a bunch rows into @databases
如果我想遍历各行,声明和使用游标是我唯一的选择吗?还有别的办法吗?
当前回答
我真的不明白为什么你需要使用可怕的光标。 但是如果你使用的是2005/2008版本的SQL Server,还有另一种选择 使用递归
declare @databases table
(
DatabaseID int,
Name varchar(15),
Server varchar(15)
)
--; Insert records into @databases...
--; Recurse through @databases
;with DBs as (
select * from @databases where DatabaseID = 1
union all
select A.* from @databases A
inner join DBs B on A.DatabaseID = B.DatabaseID + 1
)
select * from DBs
其他回答
这种方法只需要一个变量,并且不会从@databases中删除任何行。我知道这里有很多答案,但我没有看到像这样使用MIN来获取下一个ID的答案。
DECLARE @databases TABLE
(
DatabaseID int,
Name varchar(15),
Server varchar(15)
)
-- insert a bunch rows into @databases
DECLARE @CurrID INT
SELECT @CurrID = MIN(DatabaseID)
FROM @databases
WHILE @CurrID IS NOT NULL
BEGIN
-- Do stuff for @CurrID
SELECT @CurrID = MIN(DatabaseID)
FROM @databases
WHERE DatabaseID > @CurrID
END
这将在SQL SERVER 2012版本中工作。
declare @Rowcount int
select @Rowcount=count(*) from AddressTable;
while( @Rowcount>0)
begin
select @Rowcount=@Rowcount-1;
SELECT * FROM AddressTable order by AddressId desc OFFSET @Rowcount ROWS FETCH NEXT 1 ROWS ONLY;
end
Step1:下面的select语句为每条记录创建一个具有唯一行号的临时表。
select eno,ename,eaddress,mobno int,row_number() over(order by eno desc) as rno into #tmp_sri from emp
步骤2:声明所需的变量
DECLARE @ROWNUMBER INT
DECLARE @ename varchar(100)
步骤3:从临时表中获取总行数
SELECT @ROWNUMBER = COUNT(*) FROM #tmp_sri
declare @rno int
Step4:根据在temp中创建的唯一行号循环temp表
while @rownumber>0
begin
set @rno=@rownumber
select @ename=ename from #tmp_sri where rno=@rno **// You can take columns data from here as many as you want**
set @rownumber=@rownumber-1
print @ename **// instead of printing, you can write insert, update, delete statements**
end
我更喜欢使用偏移获取,如果你有一个唯一的ID,你可以排序你的表:
DECLARE @TableVariable (ID int, Name varchar(50));
DECLARE @RecordCount int;
SELECT @RecordCount = COUNT(*) FROM @TableVariable;
WHILE @RecordCount > 0
BEGIN
SELECT ID, Name FROM @TableVariable ORDER BY ID OFFSET @RecordCount - 1 FETCH NEXT 1 ROW;
SET @RecordCount = @RecordCount - 1;
END
这样我就不需要向表中添加字段或使用窗口函数。
下面是我的解决方案,它使用了一个无限循环、BREAK语句和@@ROWCOUNT函数。没有游标或临时表是必要的,我只需要写一个查询,以获得下一行在@databases表:
declare @databases table
(
DatabaseID int,
[Name] varchar(15),
[Server] varchar(15)
);
-- Populate the [@databases] table with test data.
insert into @databases (DatabaseID, [Name], [Server])
select X.DatabaseID, X.[Name], X.[Server]
from (values
(1, 'Roger', 'ServerA'),
(5, 'Suzy', 'ServerB'),
(8675309, 'Jenny', 'TommyTutone')
) X (DatabaseID, [Name], [Server])
-- Create an infinite loop & ensure that a break condition is reached in the loop code.
declare @databaseId int;
while (1=1)
begin
-- Get the next database ID.
select top(1) @databaseId = DatabaseId
from @databases
where DatabaseId > isnull(@databaseId, 0);
-- If no rows were found by the preceding SQL query, you're done; exit the WHILE loop.
if (@@ROWCOUNT = 0) break;
-- Otherwise, do whatever you need to do with the current [@databases] table row here.
print 'Processing @databaseId #' + cast(@databaseId as varchar(50));
end