Iterate through rows in SQL Server 2008

Question

Consider the table SAMPLE:

id       integer
name     nvarchar(10)

There is a stored proc called myproc. It takes only one para

Answer 1

I just declare the temporary table @sample and insert the all rows which have the name='rahul' and also take the status column to check that the row is iterated.and using while loop i iterate through the all rows of temporary table @sample which have all the ids of name='rahul'

use dumme

Declare @Name nvarchar(50)
set @Name='Rahul'
DECLARE @sample table (

    ID int,
    Status varchar(500)

    )
insert into @sample (ID,status) select ID,0 from sample where sample=@name
while ((select count(Id) from @sample where status=0 )>0) 
begin
    select top 1  Id  from @sample where status=0 order by Id
    update @sample set status=1  where Id=(select top 1  Id  from @sample where status=0 order by Id) 
end

Answer 2

If you must iterate(*), use the construct designed to do it - the cursor. Much maligned, but if it most clearly expresses your intentions, I say use it:

DECLARE @ID int
DECLARE IDs CURSOR LOCAL FOR select ID from SAMPLE where Name = @NameParameter

OPEN IDs
FETCH NEXT FROM IDs into @ID
WHILE @@FETCH_STATUS = 0
BEGIN
    exec myproc @ID

    FETCH NEXT FROM IDs into @ID
END

CLOSE IDs
DEALLOCATE IDs

---

(*) This answer has received a few upvotes recently, but I feel I ought to incorporate my original comment here also, and add some general advice:

In SQL, you should generally seek a set-based solution. The entire language is oriented around set-based solutions, and (in turn) the optimizer is oriented around making set-based solutions work well. In further turn, the tools that we have available for tuning the optimizer is also set-oriented - e.g. applying indexes to tables.

There are a few situations where iteration is the best approach. These are few are far between, and may be likened to Jackson's rules on optimization - don't do it - and (for experts only) don't do it yet.

You're far better served to first try to formulate what you want in terms of the set of all rows to be affected - what is the overall change to be achieved? - and then try to formulate a query that encapsulates that goal. Only if the query produced by doing so is not performing adequately (or there's some other component that is unable to do anything other than deal with each row individually) should you consider iteration.

Answer 3

Declare @retStr varchar(100)

select @retStr = COALESCE(@retStr, '') + sample.ID + ', '
from sample 
WHERE sample.Name = @nameparameter 
select  @retStr = ltrim(rtrim(substring(@retStr , 1, len(@retStr )- 1)))

Return  ISNULL(@retStr ,'')