Is there a way to loop through a table variable in

Question

Let's say I have the following simple table variable:

declare @databases table
(
    DatabaseID    int,
    Name        varchar(15),   
    Server      varchar(15)
)
-- insert a bunch rows into @databases

Is declaring and using a cursor my only option if I wanted to iterate through the rows? Is there another way?

Answer 1

I prefer using the Offset Fetch if you have a unique ID you can sort your table by:

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

This way I don't need to add fields to the table or use a window function.

Answer 2

Here is how I would do it:

Select Identity(int, 1,1) AS PK, DatabaseID
Into   #T
From   @databases

Declare @maxPK int;Select @maxPK = MAX(PK) From #T
Declare @pk int;Set @pk = 1

While @pk <= @maxPK
Begin

    -- Get one record
    Select DatabaseID, Name, Server
    From @databases
    Where DatabaseID = (Select DatabaseID From #T Where PK = @pk)

    --Do some processing here
    -- 

    Select @pk = @pk + 1
End

---

[Edit] Because I probably skipped the word "variable" when I first time read the question, here is an updated response...

---

declare @databases table
(
    PK            int IDENTITY(1,1), 
    DatabaseID    int,
    Name        varchar(15),   
    Server      varchar(15)
)
-- insert a bunch rows into @databases
--/*
INSERT INTO @databases (DatabaseID, Name, Server) SELECT 1,'MainDB', 'MyServer'
INSERT INTO @databases (DatabaseID, Name, Server) SELECT 1,'MyDB',   'MyServer2'
--*/

Declare @maxPK int;Select @maxPK = MAX(PK) From @databases
Declare @pk int;Set @pk = 1

While @pk <= @maxPK
Begin

    /* Get one record (you can read the values into some variables) */
    Select DatabaseID, Name, Server
    From @databases
    Where PK = @pk

    /* Do some processing here */
    /* ... */ 

    Select @pk = @pk + 1
End

Answer 3

I'm going to provide the set-based solution.

insert  @databases (DatabaseID, Name, Server)
select DatabaseID, Name, Server 
From ... (Use whatever query you would have used in the loop or cursor)

This is far faster than any looping techique and is easier to write and maintain.

Answer 4

Step1: Below select statement creates a temp table with unique row number for each record.

select eno,ename,eaddress,mobno int,row_number() over(order by eno desc) as rno into #tmp_sri from emp 

Step2:Declare required variables

DECLARE @ROWNUMBER INT
DECLARE @ename varchar(100)

Step3: Take total rows count from temp table

SELECT @ROWNUMBER = COUNT(*) FROM #tmp_sri
declare @rno int

Step4: Loop temp table based on unique row number create in temp

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

Answer 5

This approach only requires one variable and does not delete any rows from @databases. I know there are a lot of answers here, but I don't see one that uses MIN to get your next ID like this.

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

Answer 6

You can use a while loop:

While (Select Count(*) From #TempTable) > 0
Begin
    Insert Into @Databases...

    Delete From #TempTable Where x = x
End